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Scanned from the collections of The Library of Congress
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INTERNATIONAL PROJECTIONIST January 1935
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The best book ever published for the motion picture pro- jectionist. The book contains nearly 1200 pages and over 400 illustrations. Complete instructions covering the care and operation of sound motion picture equipment. All troubles that can happen to your equipment will be found listed in this book with simple instructions for the cause and remedy of same. Thousands of projectionists swear by this book.
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The Cameron books have been used for more than 18 years. They may be obtained through all motion picture supply houses, and from any bookdealer stocking technical books. Over 300 dealers throughout the world stock these books. They are a product of union labor throughout.
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\,
TERNATIONAL PROJECTIONIST
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ROJECTK
With Which is Combined PROJECTION ENGINEERING Edited by James J. Finn
Volume 8
JANUARY 1935 '
Number 1
Index and Monthly Chat 5
Formidable Opposition Develops to Electrics' Servicing 7
James J. Finn Servicing Situation Highlights 8
Something for Nothing: How Much Will It Cost? 10
J. E. Robin
Projectionists Plan Service Battle 12
Modern Amplifiers Reflect Vast Improvement in the Art .... 13
Leroy W. Chadbourne
Notes on Loudness, Pitch 15
Dr. Harvey Fletcher
Films, Radio & Television As- sayed by Dr. Goldsmith .... 16
Studios Finally Move to Correct Varying Print Densities Evil 17
Effect of Aperture Lenses on Illumination 18
Wilbur B. Rayton
The Editorial Page 21
New Vistas in Sound Trans- mission 22
Leopold Stokowski
News Notes 23
New Equipment 24
Projection Rises to New Heights in First Airplane Movie Show 26
News
Technical Hints Miscellaneous Items
Published Monthly by
JAMES J. FINN PUBLISHING CORPORATION
580 FIFTH AVENUE, NEW YORK, N. Y.
Circulation Manager, Ruth Entracht
Subscription Representatives
Australia: McGills, 183 Elizabeth St., Melbourne New Zealand: Te Aro Book Depot, Ltd., 64 Courtenay Place Wellington England and Dominions: Wm. Dawson & Sons, Ltd., Pilgrim St., London, E. C. 4.
Yearly Subscription : United
States and possessions, $2 (two years, $3) ; Canada and foreign countries, $2.50. Single copies. 25 cents. Changes of address should be submitted two weeks in advance of publication date to insure receipt of current issue. Entered as second-class matter
February 8, 1932, at the Post Office at New York, N. Y. under the act of ]&arch 3, 1879. Contents copyrighted 1935 by James J. Finn Publishing Corp. International Projectionist is not responsible for personal opinions appearing in signed articles in its columns.
MONTHLY CHAT
THANK you one and all for the nice reception accorded the last issue of I. P. Such close attention by and grand cooperation from the field cannot help but work out very well both for I. P. and its reader friends. Incidentally, can we help it if I. P.'s circulation has increased eleven per cent within the past two months, even as its advertising this month increased twenty-eight per cent?
IF THE electrics survive the cargo of poison gas unloosed in their direction upon disclosure of their "extended" serv- icing plans, projectionists will have only themselves to blame. The signing of a couple of circuits who happen to be heavily in debt to the electrics doesn't insure the success of the plan.
WHAT ever became of the grandiose plan to sell a million dollars worth of equipment to theatres through federal modernization loans? Probably those trade papers who "created" this fantastic tale will now explain why they ducked out of running follow-up stories. The story was pretty lousy anyhow, for it served only for one issue.
NEXT month will be handed down the U. S. Supreme Court decision on the Tri-Ergon mess. Should Mr. Bill Fox win out, projection rooms will witness feverish activity by the electrics to alter their heretofore well-advertised "patent- protected" sound equipments.
CONVERSION of existing low-intensity lamps for use with Suprex carbons has never appealed to us, except when the process was necessary to practically force the production of D. C. lamps in opposition to the A. C. junk then flooding the country. Now that D. C. Suprex operation is generally approved, and lamps therefor available, we can see no reason for continued use of converted lamps.
More than a year ago we counselled lamp manufacturers not to oppose con- version jobs, because the conversion job of early 1934 almost certainly meant a new lamp sometime in 1935. The sound- ness of this advice is now being demon- strated throughout the country. Why is a conversion job unsatisfactory? The detailed answer will appear herein next month. Manufacturers' orders for re- prints filled in order of receipt.
DR. A. N. GOLDSMITH certainly slaughtered the television stock pro- motors during his recent Cleveland speech relative to new advances in the electronic art, a brief resume of which appears herein. Better still, a nation- wide radio hook-up carried the good Doctor's message to a tremendous audi- ence. Which is all to the good, in view of the current activity by television stock enthusiasts.
INTERNATIONAL PROJECTIONIST
January 1935
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INTERNATIONAL PROJECTIONIST
VOLUME VIII
NUMBER 1
JANUARY 1935
Formidable Opposition Develops to Electrics' Servicing
Labor and Supply Dealers Lead Fight Against Extension of Electrics' Activities; Federal Probe Threatened
By James J. Finn
MISLEADING, misinformed, misconception and mis-statement" are a few bits of language em- ployed by the "electrics" in commenting on the exclusive announcement in the last issue of I. P. of the new all-inclusive servicing plan, covering the theatre from the roof to the cellar, sponsored by the electrics. Sig- nificantly, however, formal statements of denial were con- spicuously lacking.
I. P.'s exclusive story was picked up by the entire indus- try trade press, several of whom conveniently forgot to observe the copyright notice, not to mention the conven- tional amenities of such situations.
i In the interim there has developed formidable oppo- sition to the new servicing plan of the electrics, with dealers, manufacturers, exhibitors and Labor joining forces to resist its introduction on a general scale. Par- ticularly embittered, and very active in marshalling oppo- sition to the plan, were supply dealers, whose attitude is 'perhaps best expressed in an article by J. E. Robin, pres-
ident of the Independent Theatre Supply Dealers Assoc, appearing elsewhere in this issue.
Mr. Robin bluntly states that, failing to protect their interests by ordinary means, his members will carry the fight directly to the Government and insist upon a sweep- ing investigation of the activities of the electrics in the motion picture field. Robin also reveals Association plans for the establishment of a testing laboratory for all theatre equipment. He claims, further, that a chain servicing organization can never hope to render the same extensive quality service as can a local supply dealer.
Far less voluble than the supply dealers, but just as unrelenting and active behind the scenes in its opposition to the electrics' servicing plan, was the I.A.T.S.E., parent body of more than 25,000 projectionist and stagehand members now working in theatres throughout the U. S. and in Canada.
Following a meeting of the General Executive Board of the Alliance, devoted entirely to discussion of the danger
[7]
8
INTERNATIONAL PROJECTIONIST
January 1935
threatening its members through opera- ation of the electrics' servicing plan, International Projectionist obtained exclusively the following statement rela- tive to the official stand of the Alliance on the matter:
"The General Executive Board of the International Alliance has thor- oughly investigated the projected general theatre servicing plan. The Alliance will insist, without quali- fication, that this work be main- tained by the members of its Local organizations, and that the jurisdic- tional rights of the Alliance be fully protected. There will be no devia- tion from this policy nationally or locally.
"Intensive work looking toward the maintenance of I. A. rights is now proceeding, upon the comple- tion of which the I. A. will instruct its affiliated Local Unions."
Opposition to the plan from Labor was entirely unexpected by the electrics, and it is likely that their program will be disrupted badly as a result thereof.
No longer is it a secret, of course, that the General Office of the I. A. has been aware of the electrics' intention for some months past and has, in fact, done intens- ive investigational work in various sec- tions of the country in an effort to un- cover the true picture of the electrics' activities, some of the information ap- pearing this month and last in these col- umns being culled from this source.
Attending the session of the General Executive Board which considered the servicing problem was James J. Finn, editor of International Projectionist, who outlined his views on the matter and advocated strenuous opposition to the electrics' plans, plus the participation by I. A. men throughout the country in servicing work of every description.
Loew's Drops Erpi Service
Erpi sustained another hard blow dur- ing the month when Loew's Theatres, Inc., dispensed with Erpi service in 63 Loew theatres in the Metropolitan New York area and barred Erpi service engineers from the houses. Announce- ment of policy with respect to the other 72 Loew theatres throughout the coun- try is expected shortly, and it appears certain that Erpi will lose these accounts also.
Loew is the latest major exhibition company to adopt this course, Warner theatres having discontinued Erpi serv- ice in all its theatres on January 1 last. Significantly, the move implies no obliga- tion on the part of either Warner or Loew to purchase only Erpi replacement parts and accessories.
It became known that, subsequent to publication of the last issue of I. P., Erpi gave "verbal assurances" to I. A. officials that their "extended servicing"
plan had been misrepresented in the press and that its operation would not encroach in any way upon the jurisdic- tion of I. A. members working in thea- tres. Upon learning of this happening, International Projectionist sought to have a responsible official of Erpi re- duce this view to a formal written state- ment. The statement was not forthcom- ing, being turned aside with the answer that "Erpi has nothing to say about the servicing plan at present."
Meanwhile, even while giving "verbal assurances" of non-encroachment on projectionists' work, Erpi continued to manifest a keen interest in projection equipment and technique. I. P. learned from a very reliable source that Erpi purchased recently in New York City 20 new projector heads, possibly for their laboratory, cited in these columns last month as containing every conceiv- able type of projection equipment: lamps, arcs, carbons, generators, recti- fiers, lenses, condensers, screens, expen- sive illuminometers and other equipment.
I. P. has a complete list of all equip- ment in one such shop.
Not to mention the fact, of course, that Erpi is recorded as having pur- chased two complete sets of projector repair tools. Erpi's investment in pro- jection equipment, surveys and general preparation to date is conservatively estimated as exceeding $25,000.
The offices of I. P. were deluged with requests from projectionist organizations and individuals relating to the electrics' all-embracing servicing plan, as well as with inquiries as to how best projec- tionists could move to resist this latest threat to their security. I. P. is servic- ing these correspondents as fast as its facilities permit. Detailed reference to this phase of the situation is appended to this article.
RCA's Position
The attitude of RCA Manufacturing Co., makers of RCA Photophone sound equipment, toward the reception ac- corded the all-inclusive servicing plan by the field was in marked favorable contrast to the typical policy of silence adhered to by Erpi. A representative of RCA in the course of a two-hour session with this writer informally summed up the RCA stand as follows:
1. RCA contemplates an "extended servicing" plan, but —
2. It would be launched solely as a "goodwill" maker in the exhibition field and without additional cost to those theatres now using RCA service; and
3. The RCA plan positively would not conflict with the interests of either projectionists or stagehands, or anv other crafts, and, in fact, RCA would scrupulously avoid even an appearance of conflict; also
4. RCA does not now and will not (Continued on second page following)
Servicing Situation Highlights
Erpi's Stand
"We have no statement anent serv- icing plans to make at this time," said Erpi representative in typical fashion of avoiding enlightening comment and forcing the industry press to print the "misleading and misinformed" information which Erpi subsequently criticizes.
RCA's Stand
RCA in a frank, straightforward statement admits plans for "extended servicing" and outlines its position with respect to charges, equipment sales, and policy with respect to Labor's rights.
Loew Drops Erpi Service
The 63 Loew theatres in Metro- politan New York territory drop Erpi sound service. Loew policy with respect to 72 theatres elsewhere in country to be announced shortly. Likely will also drop Erpi service. Warner Theatres dropped Erpi serv- ice on January 1 last.
/. A. T. S. E. Stand
The International Alliance an- nounces "unqalified opposition" to any general theatre servicing plan which will threaten even remotely the jurisdictional rights of its mem- bers. Advocates handling of service, for projection and sound equipment, by affiliated Local Unions. Is now formulating policy which will govern its activities on a national scale, to be announced shortly.
Theatre Supply Dealers
Theatre supply dealers band to- gether to resist electrics' servicing plans. J. E. Robin, president of independent dealers, threatens a Fed- eral investigation of sound company activities in motion picture field. He also derides electrics' statements that service will be free and used solely to build goodwill.
Erpi's Projection Interest
Reliable reports of recent pur- chase by Erpi of 20 new projector heads in New York area; plus an- other purchase of two complete sets of projector repair tools. Laboratory housing every conceivable type of projection equipment continues to operate and acquire more equipment.
Countrywide Opposition
Projectionist organizations move quickly to offer service to theatres either free or for small charge which electrics could not possibly match. Service to include both projection and sound equipment.
January 1935
J INTERNATIONAL PROJECTIONIST
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January 1935
in the future sell any equipment that it does not itself make in its own plant, and
5. Since its servicing plan is based entirely upon its worth as a goodwill builder, extensive opposition to the plan within the field likely would mean that RCA would abandon the plan rather than have it operate to defeat the very purpose behind its introduction; and
6. RCA would readily give positive assurance on any or all of the afore- mentioned points.
Citing a paragraph in these columns last month, as follows: "If, on the other hand, such a servicing plan will not operate to encroach further upon the projectionist's domain . . . and if it will help the projectionist to produce a better show through keep- ing his equipment up to snuff by obtaining parts and effecting needed repairs — then, and only then, the plan might be acceptable to Labor," RCA holds that its plan would certainly write an affirmative answer to the fore- going ifs.
Erpi maintained a discreet silence on its intentions, as stated previously, evi- dently thinking the situation not im: portant enough to warrant a statement or being too busy furthering its servic- ing plans.
Thus it is impossible for the electrics to deny any longer that they contem- plate "extended servicing" plans. I. P.'s disclosures smoked out this fact, at any rate. In fact, Motion Picture Daily not only confirmed Erpi's servicing inten- tions but actually printed a list of names of those who will supervise such acti- vities in various territories.
With their plans uncovered and further denial of intentions being quite futile, there now remains to be answered only the question as to just how far the electrics' activities in this direction will lead.
Possible Federal Action
Should the supply dealers carry through on their threat to force a Fed- eral investigation of the electrics' acti- vities in the motion picture field, inter- esting possibilities loom up on the horizon, particularly in view of the fact that hearings on pending communica- tions legislation, in which A. T. & T., Erpi parent body, will be subjected to the glare of the publicity spotlight, will be begun in Washington early in February. A rumpus in the picture field, in which an A. T. & T. subsidiary was involved, might affect adversely the communications interests of A. T. & T.
It is no secret, of course, that supply dealers throughout the country are lin- ing up support for their cause and urging that pressure be put on Wash- ington legislators to the end that the communications investigation be sup- plied with ample funds and backed to the limit. This is only one phase of the dealers' attack on the general servic-
SOMETHING FOR NOTHING: HOW MUCH WILL IT COST?
J. E. Robin
PRESIDENT, INDEPENDENT THEATRE SUPPLY DEALERS ASSOCIATION
IN THE December issue of this publica- tion, James J. Finn analyzed the pro- jected super-servicing plans of the "elec- trics" and pointed out clearly that pro- jectionists and stagehands could not but be unfavorably affected by this develop- ment. Mr. Finn could not, of course, dwell at great length on the position of the dealers and the manufacturers in this dangerous situation. It is, there- fore, a privilege to accept his invitation to state the case of these two groups, particularly the first-named.
We have been reliably informed that the "electrics" intend to furnish this remarkable service at no cost to the exhibitors and purely for the purpose of developing "goodwill." This is really too good to be true and makes us wonder whether the millenium has arrived.
We would not think of intimating that this magnanimous and well-meaning cooperation is inspired by any ulterior motive. But history has a way of re- peating itself, and our memory of what happened with regard to sound apparatus somehow makes us feel that the super- servicing plan is only the first step in the wrong direction, that is, as far as dealers, manufacturers, exhibitors and Labor are concerned.
Manufacturers' Stand
Now, will the manufacturers jump at an opportunity to sell to the "electrics" quantities of equipment that will no doubt exceed those that the independent dealers could absorb? Of course, they will; but we maintain that they would eventually regret the adoption of such a policy. Again, experience supplys us with the answer. It will be but a short while before the "electrics" will be turn- ing out all the various forms of equip- ment that their servicing will require. Logically, what is the next step?
It requires no great amount of in- telligence and imagination to paint the
ing plan. If, on top of this, Labor should utter a few deep-throated and well-directed growls at the psychological moment, the electrics might find them- selves in pretty deep water, speaking in terms of public relations.
International Projectionist is ad- vocating intense resistance by Labor, supply dealers, manufacturers and others to any extension of theatre servicing by the electrics. In fact, this publication is not content that the opposition con- fine itself merely to resisting an "ex-
picture. It is unavoidable that the ex- hibitors who have been the recipients of this "free" and all-embracing service will show their deep appreciation by fol- lowing the "recommendations" of the "electrics' " experts and purchase from the latter the parts and equipment which they may (or may not) need. This will leave the manufacturers out in the cold without even the possibility of turning to the independent dealers who, by that time, will have been entirely squeezed out of the picture.
It is a well-known fact that rca and erpi have for some time past been sell- ing complete projection and sound equip- ments for industrial use, schools and others which may be classed as the non- theatrical field. In many instances, the projection equipment, with the exception of the sound apparatus and screens, has been procured from a dealer, and on almost all jobs the sale has been made by the "electrics" and billed by them.
The RCA Radiotron Co., Inc., tube manufacturers and a unit of the RCA Manufacturing Co., are so concerned with the welfare of the independent theatre supply dealers that they have been selling Radiotron tubes at list less 40% to theatre owners who have signed a contract covering their tube requirements for one year. The distributors, who have an overhead and a payroll to meet, can- not in many instances buy these tubes for resale on a competitive basis.
Eliminate Service Charges If the "electrics" are so interested in building up "goodwill" that they are de- sirous of rendering a free consulting service in addition to the regular in- spection and maintenance service agree- ment that they have, it occurs to us, as businessmen, that they could do this much more expeditiously and effectively by eliminating the service charge on {Continued on page 34)
tension" of electrics' servicing, but is backing the plan of projectionists tak- ing over the servicing not only of pro- jection equipment but of sound systems as well.
With a large majority of electrics' contracts now expiring, or already ex- pired, I. P. advances the thought that there will never exist a better time than the present for projectionists to move in and displace the sound system engineers. This publication holds that this new servicing plan is merely the
January 1935 INTERNATIONAL PROJECTIONIST 11
Still
UNIQUE
WHEN it was introduced in 193 1, Eastman Super-Sensitive Panchro- matic Negative was definitely a "new and different" product. And there is still no other film like it. ..no other has wrought compa- rable changes in motion picture procedure, or contributed as much to motion picture quality. It is only natural that this Eastman film should be unique, also, in the enthu- siasm which it continues to arouse among cameramen and producers. Eastman Kodak Company. (J. E. Brulatour, Inc., Distribu- tors, New York, Chicago, Hollywood.)
EASTMAN Super-Sensitive Panchromatic Negative
12
INTERNATIONAL PROJECTIONIST
January 1935
last-ditch fight of the electrics to retain their identity as a theatre servicing or- ganization, with its (to date) lucrative pickings — straight equipment sales of sound equipment today being mostly re- placement jobs.
Sink-or-Swim Situation
Further, I. P. points out, now is the time for direct action by projectionists and others on a basis of sink-or-swim - — the sinking to happen if the electrics are permitted to write thousands of con- tracts now for an indefinite number of years. Either projectionists get out now and take control of matters, is the view of I. P., as they should have done in 1927-28, or forever be relegated to a position of secondary importance in the theatre field.
An encouraging feature of the mass of letters received by I. P. from pro- jectionist organizations throughout the country, relative to the servicing situa- tion, is the widespread mention of the need for more activity along technical lines by the organized projectionist, either through some national technical organization or direct from the General Office of the I. A. Previous efforts to form and maintain some such organiza- tion have been made, dating back to 1928, but the need for such cooperation evidently was not acute at that time and the then existing societies and groups were allowed to languish.
Announcement that several I. A. units are already engaged in general theatre servicing work, including sound systems, came as a surprise to a majority of Local Unions. Only Cleveland and San Fran- cisco have been cited in previous articles herein, yet there are at least ten other cities where Local Unions are engaged in servicing work.
Cleveland's theatre servicing work by projectionists dates back to silent pic- ture days, thus it is not new, the Local there incorporating the service, which is free, into its contract for Labor. Equipment breakdowns are reported direct to an office maintained by the Union, several members of which are always on call. A small truck, cap- able of carrying all necessary equip- ment, is used, and spare heads, jaws, lamps, lenses, batteries — in fact, all necessary equipment — is included.
Cleveland theatres would never think of calling anybody but the Union man in the case of a breakdown or any trouble, whether in the sound or the projection equipment.
San Francisco's service work started at the time the original RCA servicing contracts expired. At the invitation of RCA, Local 162 agreed to assume the servicing of several theatres. The RCA service engineer, who happened to be a member of an eastern Local, was taken
over by the Local. Expecting to suffer a loss on this service man, Local 162 was agreeably surprised after two years of service work to find that his opera- tions had netted a small profit — even after the expenditure of $500 for a test set and proper servicing tools and equip- ment.
New theatres were continually added to the Local's service roll, with the small independent exhibitor welcoming the opportunity to get immediate sound service at a cost of one-third what he formerly paid to the electrics. Local 162 did not enter upon servicing work to make money, or even to gain man- power, its attitude being that such action was the very best insurance in the world against any encroachment upon its jurisdiction.
Several interesting angles present themselves relative to such servicing activities by Local Unions:
1. Should the service be free, or should there be a charge made for the costs involved, wages, equipment and upkeep? The answer to this question naturally depends upon prevailing con- ditions in the various localities.
Obviously, the electrics cannot afford to render service without cost; but the Local Union can, charging the cost to job-insurance, or security-insurance. But should the service be free? It appears that such Locals as are now rendering service have no trouble at all in getting paid for it, the price always being kept
below the lowest level possible for the electrics to establish. Such income will go toward paying the cost of Local servicing operation, and might even net a small profit, to which no exhibitor would object provided his costs were being sharply cut below the electrics' figures.
2. The angle of existing servicing contracts should be carefully investigated before a Local assumes servicing of a given theatre. This is important.
3. Competency is a vital considera- tion. The work rendered by the Local should be on a par, from the standpoint of quality and promptness, with that rendered by the electrics. While im- portant, this shouldn't prove too hard a nut to crack, since Local service men would not be interested in "forcing" the sale of equipment and parts.
4. The necessity for proper test equipment. The very same equipment now used by the electrics' service engineers, about which there is no mystery and which is easily obtainable in the open market, could be utilized by the Local. In fact, the S. M. P. E. visual and sound test reel, prepared by projection men within the Society, is now utilized by the electrics and is avail- able to anybody who wants it. In addi- tion, the Local service man would have the advantage of complete cooperation on the part of the projectionists, from his own organization, working in the theatre.
Projectionists Plan Service Battle
INDICATIVE of the attitude of projectionist organizations throughout the country on any extension of servicing activities by the electrics, and reflecting the influence of I. P. in spurring projectionists to action, is the following letter which is representative of a mass of letters anent this topic received by I. P. :
Editor, I. P.
Sir: I am planning a meeting of several projectionist groups for next Sunday to consider this whole proposition of projection and sound equipment servicing. I am sure that you can be of great help in supply- ing data and advice as to the best procedure for us to follow.
I am reluctant to ask so much from you, but then that is what you get for being so "doggone" efficient and getting the dope before anybody else.
As I see it, projectionists have been snoozing for too long and have slipped a good bet by not taking a servicing proposition to the managers long before now. I believe that there is yet time to get down to business and put this thing over for ourselves.
Like all other sections of the country we drifted along from day to day, with some of the men apply- ing themselves diligently and others just sitting back and letting the parade of progress pass them by. Now is the time for concerted action
throughout the country, unless we all want to sink together and let others step into our places. The good men within our ranks will just have to exert themselves and pull the others to safety. If given the chance I think that our men can show the managers just as good, if not better, work than other service groups.
Now is just the time when we could use a strictly technical organization of projectionists, the value of which when they were functioning the men seemed strangely unable to appre- ciate. Right now is when we would be collecting royalties in profusion through the existence of such a body. Couldn't you apply your fine talents to reviving such a plan?
In closing, I think that projection- ists have finally bestirred themselves into action, and you are the guy who supplied the spark to explode the bomb under them.
Charles E. Curle
Secretary, Local 259,
Chattanooga, Tenn.
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INPUT FKOM R£PROPUCER EQUALIZER
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AMPLIFIERS
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IMPROVEMENT IN THE ART
I HE full extent of the changes that have taken place in the design of theatre amplifiers during the last few years cannot be appreciated until the old and new are placed side by side, as in Figures 1 and 2. Only by carrying the comparison down to small details can the projectionist realize what these changes mean to his work and to the nature of his responsibility.
Figure 1 represents one of the very first amplifiers used for theatre sound. Some of these amplifiers are giving satis- factory service even today in large de- luxe theatres.
The filament circuits of this amplifier begin at the bottom center of the draw- ing, with two terminals marked " — 12V" and "+12V". The line from the positive terminal runs up, right, up, right, up an inch, right an inch and up an inch to the positive terminal of the filament of the extreme right-hand tube. Through this filament, then down, left and up to the fil- ament of the center tube. Through this and down, left, down and right to "Filament 2 & 3 Jack", which is an arrangement for plugging an ammeter in series with the filament circuit to read the filament cur- rent.
From this jack to the double winding of the retardation coil. Thence down and left to "Filament 2 & 3 Rheostat." Thence to the negative terminal at the bottom of the drawing, through a three- ampere fuse.
This filament circuit has a branch line
Leroy W. Chadbourne
that supplies the extreme left-hand tube. From the positive terminal up, right, up, right, up an inch and then, instead of turning right, follow the other branch left about two inches, thence up an inch to the positive side of the filament. Through the filament, left through the grid bias resistor, and down to "Fila- ment 1 Jack". Through this, through the retardation coil, through "Filament 1 Rheostat", and then down and right to the 3-ampere fuse and negative.
The source of power for this circuit is external, and consists of 12-volt storage batteries, although at present it is com- mon practice to use a rectifier.
The source of plate power originates, as far as this amplifier is concerned, with the other three terminals at the bottom of the drawing, marked "G", " + 130V." and " + 350V." Beginning at the high voltage end, the line may be traced upward through the quarter-ampere fuse to "Plate 3 Jack", thence through the re- tardation coil to the plate of the right- hand tube. From the filament of that tube back to the positive terminal of the
NOTE: The drawings in this article are intended only to aid the reader in contrasting new and old amplU fiers, and in no wise are they indi- cative of the present relative merits of various sound equipments. — Edi- tor.
[13]
filament circuit, which is shorted to "G".
The 130-volt line for the other two tubes has two branches. From the 130- volt terminal up, right, up, right and up past the filter condenser, then left, and up to "Plate 2 Jack". Thence up through the retardation coil to the plate of the middle tube, and back to "G" through the filament circuit.
Instead of turning upward at "Plate 2 Jack" the other branch of this line may be traced leftward from the junction point below that jack and into "Plate 1 Jack". Thence upward through the coil marked "Input Transformer" to the plate of the left-hand tube.
In the lower right-hand corner of the drawing, just above the plate power in- put terminals are four terminal posts, "A", "B", "C", and "D". Just below these are three resistors. This arrange- ment is included to provide for a second type of plate power input.
The plate power for this amplifier was provided in two different ways. One was to use a 350-volt bank of glass-case stor- age "B" batteries. In that case the full 144 cells were connected to the " + 350V" tap, and a branch connection was taken at the sixtieth cell for the " + 130V" tap.
In other installations, plate power was derived from a vacuum-tube rectifier mounted on the amplifier rack alongside of Figure 1. In that case the " + 130V" and "+350V" terminals were not used. Two wires, + and — 350 volts d.c. led from the rectifier. The negative line
14
INTERNATIONAL PROJECTIONIST
January 1935
was connected to "G" and the positive wire to "D". Jumpers were then added to connect "D" to "C", and "B" to "A". The three resistors then constituted a voltage divider bridging the plate line, and the drop through the two right-hand resistors reduced the voltage to 130 at the point where "A" connects.
The grid bias of the right-hand tube is secured as follows: From the negative leg of the filament down, left, down and left to the positive terminal of the 27-volt "C" battery. This consisted of a bank of flashlight type dry-cells fitting into a battery box that mounted on the front panel of the amplifier. From the top or negative terminal of that battery right through "Z" and "Y", and upward through the coil marked "Input Trans- former" to the grid of the tube. The bias of this grid was then 27 volts plus half the drop through its filament — that is, it was while the batteries remained fresh.
The bias of the center tube may be traced from the positive leg of its fila- ment to the bottom or positive side of the grid battery. Thence leftward through the lSV^-volt connection, and up through the "Gain Potentiometer" (volume con- trol) to the grid of the tube. The bias of this tube, with batteries in good con- dition, is therefore 13.5 volts minus one- half the drop in the tube filament.
The bias of the left-hand tube is ob- tained without grid or "C" batteries. The bias resistor connects to the negative side of the filament. It is in the negative leg of the filament supply, and the voltage
drop through it provides bias for the grid.
The speech input to this amplifier is at terminals 1 and 2, at the extreme left of the drawing. The voltage ratio of this transformer is governed by the "Low- High" volume control switch. This is mehanically connected with the "Gain Potentiometer" in the following stage, and throws over automatically when that potentiometer is moved from Point 11 to Point 12. This would seem to mean, according to the drawing, that the direction of the motion of the sliding contact is reversed, but actually the knob can be turned continuously from Point 1 to Point 22, exactly like any other vol- ume control.
The d.c. component of the plate cir- cuit of the left-hand tube returns to the filament through the source of "B" sup- ply and the common connection between "G" and "+12V." The a.c. component is by-passed through the condenser shown just above terminals "A" and "B". That branch of the a.c. component that runs through the coupling condenser continues back to the filament through the gain potentiometer and the grid battery.
The coupling arrangements between the second and third tubes, and the third tube and output, are essentially similar. The a.c. component of the output stage, so far as any of it flows through the re- tardation coil, returns to the filament through the source of "B" supply; while the branch through the coupling con- denser returns direct. The output cir- cuit resistor is used or omitted according
to the number and type of power ampli- fiers following, and their input imped- ance.
The responsibilities imposed on the projectionist by the amplifier shown in Figure 1 are approximately as follows:
1. Charge storage "A" batteries.
2. Charge storage "B" batteries, if used.
3. Clean and water all storage bat- teries (a total, with "B" batteries, of 150 cells) .
4. Observe that tubes are lighted.
5. Read plate and filament currents occasionally by plugging meter cords into the five jacks.
6. Readjust two filament rheostats as condition of storage battery varies,
7. Test "C" battery voltage with portable voltmeter.
8. Clean "C" battery contacts,
9. Clean contacts of filament rheo- stats and meter jacks.
10. Clean tube socket contacts.
.
The Circuits of Figure 2
With Figure 1 being representative of 1928, Figure 2 is a typical example of the modern 1935 amplifier.
An outstanding difference between these two circuits is that, so far from needing storage battery or other external power (except 110-volt line a.c), Figure 2 supplies both high voltage d.c. and low voltage a.c. to other circuits outside itself.
The a.c. supply is indicated by the receptacle circle at the lower right of the drawing, some distance left of the 5- terminal connection block. The 110-volt
|
INPUT |
TRANSFORMER |
|
TERM, 1 TERM. |
WORK PROM IMPEDANCE |
|
1 TO 4 |
SOOIL |
|
Z TO 1 |
2 50H- |
|
OUTPUT |
TRANSFORMER |
|
TERM 1 TERM |
WORK INTO IMPEDANCE |
|
1 TO -J |
soon. |
|
1 TO £ |
I5JL. |
Q\
J unitary 1935
INTERNATIONAL PROJECTIONIST
15
circuit runs down and left to the tapped primary of the power transformer. The right-hand secondary of this transformer provides low voltage power to terminals 4 and 5 of the connection block just men- tioned, for use outside this amplifier. That power lights the signal lamps of the remote volume control used with this amplifier.
The volume control itself is the 500,- 000-ohm resistor R-23, shown just left of the Type 56 tube in the center of the drawing. The sliding contact is moved by a small a.c. motor that can be operated from a remote location. A bank of signal lamps at the operating point indicates its setting. The right-hand secondary of the power transformer lights those lamps.
There are no rheostats and no meter- ing arrangements in the filament cir- cuits of Figure 2. The heaters of the two left-hand tubes, types 24-A and 56, are powered by the extreme left-hand secondary of the line transformer, which is also capable of supplying additional current at the same voltage to a single- stage pre-amplifier through terminals 6 and 7 of the connection block in the ex- treme lower left-hand corner.
The filaments of the push-pull type 45 tubes are heated by the second secondary from the left. There is no occasion for filament rheostats or meter readings, be- cause the filament voltage will always re- main the same while the power line volt- age stays constant. The tap switch in the primary of the power transformer can be set to compensate for high or low voltage lines. The filaments of the tubes and the operation of the amplifier are not troubled by minor variations in the heating current. Wide fluctuation of power line voltage is, of course, another matter, to be cared for by installation of voltage control equipment.
The plate power of Figure 2 is derived from the full-wave rectifier tube, type 80. The positive output is, of course, at the filament. The line may be traced right, and then upward through L-8 and L-9, past the filter condensers C-20, C-21 and C-22. From the top of coil L-8 one branch can be traced right and then upward to the center tap of T-4 primary; thence to the grids of the push-pull stage. From the filaments of that stage to the center tap of R-27, through the bias resistor R-28. From the ground connection at the negative side of that resistor to the ground connection just right of Resistor R-24, about two inches left of the lower push-pull tube. Thence left and down, past the filter condensers, to the mid-tap or negative of the plate secondary of the power transformer.
Returning to the mid-tap of the push- pull output transformer T-4, another branch may be traced upward and left to the top of R-26, down through R-26 to the plate of the type 56 tube. From the cathode of that tube down through L-31,
and right and down through the bias resistor R-24, thence left and down to the center-tap of the plate secondary.
Still another branch runs left from the top of R-26, down through R-19, and left through R-20 to the screen grid of the type 24A tube. Still another branch, following the positive line across the ex- treme top of the drawing, runs downward through R-16 and R-17, right, up, right, down through R-81, and R-18 to the plate of the type 24A. One more branch runs down through R-12, left, down and left to the " + 90" terminal of the left-edge con- nection block. This provides bias volt- age for two photoelectric cells.
The grid bias of the push-pull tubes is furnished by the voltage drop through R-28 (just left of T-4), which is in series with the plate current through those tubes. The grids return to the negative side of that resistor through the common ground connection.
The bias of the '56 tube is supplied by the voltage drop through R-24, through which the plate current of that tube re- turns from cathode to ground. The grid of the same tube is connected to the ground or negative side of R-24 through the volume control potentiometer. The bias of the control grid of the '24 tube is derived from the drop through R-21, to which the control grid connects through the secondary of the input transformer, T-2.
Speech Circuits of Figure 2 The speech input to Figure 2 is through the four upper terminals of the left-hand connection blocks. The first and fourth are the photo-cell input line, the other two being used for special in- puts, as from announcing microphone. C-10 and R-15 are part of the elaborate frequency-controls of this amplifier. The plate of the 24-A type tube is coupled through C-14 to the volume control po- tentiometer R-23, the drop across which is applied to the grid of the second stage,
type 56 tube. C-ll and C-23 are fre- quency control condensers.
The speech component in the plate circuit of the '56 tube may be traced upward through L-7 and down through C-19, thence through the primary of coupling transformer T-3, and back to cathode. L-6 and L-7, C-17 and C-18 are frequency control devices. The input to the push-pull stage is from transformer T-3, and the output through T-4, the sec- ondary of which is designed for imped- ance match to the power amplifier fol- lowing. It is also provided with a tap connection through which it can be coupled directly to the speakers in emergency.
The manner in which the frequency control devices seen in the speech cir- cuits of this amplifier can be adjusted in the theatre to adapt its characteristics to acoustical conditions, recording tech- nique, and other variables not control- lable in the factory, is explained in de- tail in the manufacturer's instruction book, which accompanies each installa- tion. Such elaborate controls were not provided in 1928. The amplifier shown in Figure 2 requires of the projectionist only the following:
1. Throw main line switch on in the morning and off at night.
2. Use of more elaborate test equip- ment, requiring real electrical knowl- edge, to find trouble.
3. Understanding of tube types and circuit arrangements not used in earlier equipment.
From these illustrations and the dis- cussion of them the meaning that im- proved amplifiers have for the projec- tionist should be obvious. They mean less trouble but more responsibility. Or, to attempt to sum up the difference in a phrase, they substitute the requirement of better and more thorough electrical knowledge for those of cleaning storage battery tops and adjusting rheostats.
NOTES ON LOUDNESS, PITCH
Dr. Harvey Fletcher
BELL TELEPHONE LABORATORIES
MUSICIANS employ three terms to describe different aspects of the sensation they experience when listening to musical tones. These are pitch, loud- ness, and timbre, although the term qual- ity, or tone color, is sometimes substi- tuted for timbre. Most textbooks on physics have taught that these psycho- logical characteristics are related in a simple way to three corresponding phy- sical quantities: frequency, intensity, and overtone structure.
The relationship between pitch and fre- quency, and between loudness and in- tensity, has been thought to be one of
direct correspondence: the pitch of each note corresponding to a definite fre- quency, and the loudness of each note to a definite intensity. The relationship be- tween harmonic structure and timbre has had no such simple formulation, but at least the timbre has been thought to de- pend on overtone structure alone.
Bell Laboratories Studies
Studies in these laboratories, however, have shown that no such simple relation- ships exist, that each of the psychologi- cal quantities — -although depending chiefly on the corresponding physical
16
INTERNATIONAL PROJECTIONIST
January 1935
quantity — actually depends on all three. That there has not been a strict one-to- one correspondence between loudness and intensity has been known for some time, but only recently has accurate quantitative data been obtained. Be- tween pitch and frequency, on the other hand, it is generally thought that there is a strict one-to-one correspondence.
Frequency is the number of vibrations per second made by the sound source, such as a tuning fork or a violin string. Most musical tones, however, are com- posed of a series of frequencies which are multiples of the lowest or funda- mental. For such tones the frequency of the fundamental is considered as the frequency of the tone, while the number and magnitude of the harmonics pro- duce the overtone structure that results in the perception ot a definite timbre.
The intensity of the tone is the power content of the air vibrations at the posi- tion where the listener hears the tone.
Among musicians loudness is roughly gauged in seven steps running from ppp (pianissimo) to fff (forte). Such a scale is entirely inadequate for scientific stud- ies, both because the steps are too large and because there is no definitely estab- lished reference loudness.
To provide a more suitable measuring scale, it has been the practice for some time in the Bell Laboratories to measure loudness in terms of the power intensity of a pure tone at a frequency of 1,000 cycles per second. Because of the wide range of intensities to which the ear re- sponds, it has been convenient to use a logarithmic scale of values.
The use of such a scale is further justified because the minimum change in intensity that the ear can detect seems to follow more nearly a logarithmic than an arithmetic law.
Although no quantitative measure- ments have been made upon the timbre of a musical tone, we know that it de- pends not only upon the overtone struc- ture but also upon the intensity. If a violin tone, for example, is reproduced at a very much higher intensity than that at which it is usually heard, it will be very evident that the timbre is changed.
A scale for representing timbre is now being worked out and it will be interest- ing to see if some quantitative measure- ments similar to those reported under loudness and pitch can be made to de- scribe the quality aspects of the tone. It is sufficient to say here that there is no doubt but that the results will show that timbre is dependent not only upon the overtone structure but also upon the intensity and the pitch of the tone.
It is thus a safe conclusion that each of the three psychological characteristics of a tone is dependent on all three of the physical characteristics, although the in- fluence of one is predominant in each case.
FILMS, RADIO AND TELEVISION ASSAYED BY DR. GOLDSMITH
SPjcAKiNG through a tiny microphone no larger than a matcnfcox, iastened to his coac lapel, a device he described as "permitting one man to be heard above a multitude", Dr. Alfred N. Gold- smith, noted scientist and consulting en- gineer of the RCA Manufacturing Com- pany, described and demonstrated recent- ly some late scientific developments from the leading radio research laboratories to more than 400 guests of the Cleveland Chamber of Commerce. The address was broadcast over a nationwide radio hook- up.
The lapel microphone worn by Dr. Goldsmith utilizes the "velocity" princi- ple of operation in which reproduction is obtained by the varying impact, or velocity of the human voice on a sensi- tive metallic ribbon within the mechan- ism. With this device a public speaker can move about freely without impairing the quality of the sound.
Pointing out that we already hear and will eventually see by radio, Dr. Gold- smith suggested that in the remote future radio might appeal to man's other senses, such as touch, taste and smell. For example, he said, there was the possi- bility of transmitting three-dimensional replicas of objects in the studio through "Teletactile Broadcasting", so that a solid representation which "might even be touched as well as viewed could be sent into the home." "Telegustatory Broadcasting", or the transmission of taste, might make it possible to "taste" a fine brand of coffee, for instance, by radio. The transmission of smells would perhaps be easier, he said, since the "Telolfactory" receiver need only spray into the air a duplicate of the odor trans- mitted. He emphasized, however, that these possibilities were now "only whim- sical and remote imaginings".
Sound Picture Progress
To illustrate the remarkable progress which has been made in improving the quality of sound motion pictures, Dr. Goldsmith demonstrated for the first time in public a radically new system of high quality sound-on-film recording which, according to RCA engineers who devel- oped it, will be the "motion picture sound of tomorrow", because it com- pletely eliminates background hissing noises and, theoretically, makes possible the ultimate of realism in sound-on-film recording and reproduction.
Using a special film recording of a musical performance in the Radio City Music Hall in New York, Dr. Goldsmith called attention to the ability of the new system to reproduce the full definitions
and shadings of all the instruments in the orchestra over the complete audible range of sound, as well as to the com- plete absence of hiss during the quieter portions of the music. With the new recording method, the sound waves are halved into two separate but symmetrical sound tracks, one negative and the other positive, automatically eliminating the unused portions of the sound track which is a necessary part of all existing sound- on-film systems.
Speaking of the development of fac- simile picture transmission, or the trans- mission of "still" pictures by radio, Dr. Goldsmith said that ultimately facsimile transmission will become a public broad- casting service of great popularity. Any printed or pictorial material will, sooner or later, be capable of speedy transmis- sion instantaneously into a multitude of homes provided with simple automatic- ally-functioning receiving equipment.
While describing the steady and order- ly development of television experiment- ally as amazing, Dr. Goldsmith felt it necessary to temper optimism with a note of restraint in discussing the future of television broadcasting. The problems of television extend beyond purely technical considerations of transmitter and re- ceiver, he said.
There is the tremendous economic problem of launching a nationwide tele- vision service, when the cost of connect- ing numerous broadcasting stations of only limited service range in a network is at present staggering. Then there is the question of supplying almost overnight a demand for talent which will be pleas- ing to the eye as well as the ear in such quantities as would drain the available supply in Hollywood, for instance, in a very short time. Then there is the import- ant question of who will pay for the high cost of putting this talent on the air, for commercial sponsors would be called upon to pay a substantial portion of the cost of a feature-film production for an hour's broadcasting. That these prob- lems will be solved in time Dr. Goldsmith did not doubt, but it is evident, he said, that much must yet be accomplished in the interim.
A remarkable new device called an os- cillograph was connected to a number of radio receivers to permit everyone to "see" the characteristics of the human voice or other sound in the form of fluctuating waves. A stream of electrons, otherwise known as a cathode ray, paints a continuous picture of the sound waves on a glowing, or "fluorescent" screen. The oscillograph, according to Dr. Gold-
January 1935
INTERNATIONAL PROJECTIONIST
17
smith, is expected to become to electrical, physical and mechanical research and development what the X-ray is to diag- nosis in medicine. Originally designed for radio service men and engineers, it is finding seemingly limitless applications in many other fields, including certain phases of the aviation, automotive, and public utility industries.
Other new devices described by Dr. Goldsmith were a new type of radio tube, resembling an acorn in size and shape, for use by radio amateurs and experi- menters in exploring the possibilities of the ultra-short micro radio waves; an amateur sound camera which makes it possible for anyone to make his own
sound movies as easily as silent movies; a small chest, resembling a cigar humi- dor which when connected to any elec- trically operated radio receiver converts it into a phonograph combination instru- ment. It can be played from a conven- ient chair at a distance from the re- ceiver to which it is connected. Also, a "Caruso record which Caruso never heard", a phonograph record which in- genious engineers have been able to literally recreate from the original one made by Enrico Caruso so that now many years after his death Caruso's immortal voice may be heard with a new brilliance to the accompaniment of a large modern orchestra.
Studios Finally Move to Correct Varying Print Densities Evil
STUDIO laboratory and camera de- partment heads met recently at United Artists Studios to witness a screen illumination demonstration pre- pared by the Academy Research Council consisting of sample prints from each studio, projected at various high- and low-intensity illuminations, and designed to demonstrate the difference between the illuminations on the screens in the Holly- wood studio viewing rooms as compared with theatre screen illumination through- out the country.
The demonstration is part of the in- . vestigation which has been going on for some months on the feasibility of bring- ing studio projection room screen illum- ination characteristics closer to the con- ditions prevailing on the theatre screens, and is important because of the fact that pictures made in the studios are judged, insofar as camera and laboratory work is concerned, on screens which in many cases are considerably brighter or duller than the theatre screens upon which the public will later view the same picture.
Studio Questionnaire
At the conclusion of the meeting, each technician present was given a question- naire and asked to write up his ideas and opinions of the demonstration, for use by the subcommittee in preparing their final report for presentation to the Re- search Council and the producing com- panies.
Print density has long been a problem of major importance in the projection field. The Projection Practice Commit- tee of the S. M. P. E. has repeatedly urged that an investigation of West Coast print procedure be made with a view to effecting improvements in exhibition. Fol- lowing is an excerpt from the Commit- tee report for 1932:
"It has been definitely established that the intensity of screen illumination in most studio projection rooms is greatly in
excess of the intensity that can be ob- tained in theatres. The great disparity existing was pointed out in a report of the Theatre Lighting Committee pub- lished in the February, 1931, issue of the S. M. P. E. Journal.
"Complaints regarding dense prints persist, however, indicating the need for additional emphasis in the matter.
"The Projection Practice Committee has conducted a partial survey of typical theatres for the purpose of determining the values of screen illumination obtain- ing in practice, and it is significant that its findings, in a widely separated terri- tory and after a lapse of two years, check closely with the findings of the Theatre Lighting Committee previously referred to.
"The results of these two independent surveys indicate that the average intens- ity of the projected light at the surface of theatre and screens lies between 8 and 12 foot candles, and that the average coefficient of reflection is about forty per cent, corresponding to intensities be- tween 3.2 and 4.8 foot-candles, these fig- ures being based on the use of diffusive screens.
"In tests made by the Committee, each projector was equipped with a two-blade 90-degree shutter which caused a reduc- tion of approximately 50 per cent of the screen illumination, as compared with measurements made when the projector was at rest. In each test the auditorium illumination approximated that obtaining during the presentation of pictures.
Studios vs. Theatre Practice
"Invariably much smaller pictures are projected in the studio projection rooms than in the average theatre, resulting in excessive screen illumination. In addi7 tion, reflective screens are sometimes used in studio rooms, adding further to the brightness of the picture. In the great majority of theatres, however, not only are much larger pictures projected than are shown in the studio rooms, but diffusive screens are used.
"Obviously, under such circumstances it is extremely difficult to reconcile studio
'screen values' with theatre 'screen values', unless some compensating ad- justment is made in the studio room. It seems highly desirable that no reflective screens be used in studio rooms in which print density is to be judged.
"On the basis of these facts, therefore, and in view of the easy and inexpensive manner in which the requisite change can be made, the Committee suggests that in each studio projection room where the screen illumination is exces- sive, each projector be provided with a diaphragm or iris in front of the lens to reduce the flux of projected light while measurements of screen illumination are made.
"The iris can be so adjusted that the screen reading approximates the average value obtaining in theatres, after which a diaphragm mask having a fixed aperture of the proper size can be substituted at will for the iris."
S. M. P. E. Now Official Standards Body
The S. M. P. E. has been named sponsor of a sectional committee now being organized by the American Standards Assoc, to work on standards for motion picture apparatus. Regard- ing this work, the Association com- mented :
"A sectional committee is now being organized to work on standards for mo- tion picture apparatus, the S. M. P. E. having been named sponsor of the com- mittee. The scope of the work has been defined as 'Terminology, Dimensional Standards, Methods of Test and Rating, and Performance characteristics of the materials and devices used in sound mo- tion picture photography, and in sound recording, processing, and reproduction in connection therewith.'
Representative Group
"The organizations invited to name rep- resentatives on the committee include technical or engineering societies inter- ested in motion pictures, electricity, radio, acoustics, fire protection, lighting, and optical science, manufacturers and distributors of kodaks, films and other equipment, theatre owners, exhibitors, producers and distributors, and U. S. Government departments."
Propose Senate Inquiry of A. T. & T. and Affiliates
Investigation of the American Tele- phone & Telegraph Co. was proposed in a joint resolution introduced on Jan- 24 by Senator Wheeler and Representative Rayburn, chairmen of the respective Interstate Commerce Committees, accord- ing to an Associated Press dispatch from Washington.
The resolution calls for an appro- priation of $750,000 and would enable an extensive inquiry into the communi- cations field, including an investigation into so-called propaganda issued by A. T. & T. and also into the workings of its various subsidiaries.
EFFECT OF APERTURE LENSES ON ILLUMINATION
Wilbur B. Rayton
THE illumination of a projected motion picture image for any given combination of light source, light collector, and projection lens is a subject so complex that any approach to full comprehension of all its details can be attained only after prolonged study. This fact may be responsible for the proposal of numerous schemes for improving illumination, either by in- creasing its total quantity or by improv- ing its distribution, that at first sight look plausible, but do not always work out as expected.
It is to the application of one such proposal in the projection of standard 35-mm. film that attention is here di- rected. It is a suggestion the principal aim of which is to improve evenness of illumination. Since relatively few have occasion to keep in mind all the details of motion picture illumination, it seems advisable first to outline briefly the two types of illuminators in com- mon use.
The ideal illuminator for motion pic- ture projection would be a light source of uniform and sufficient brightness and as large as the aperture in the film gate, but not so hot as to damage film when placed practically in contact with it. If such a light source were available, a motion picture projector would reduce to the form shown in Fig. 1. Illumination would be even over the area of the picture except for two facts, one of which we shall ignore, and the other of which is demonstrated in the figure.
Reversing the Light Path
It is much more convenient in study- ing this problem to think of the light sometimes as traveling from the screen to the film; at other times it may be more convenient to think of it as travel- ing from the light source to the screen, in the normal manner. The reversibility of a light path makes such a procedure entirely justifiable. At present we shall
Projection optics is the most gener- ally misunderstood link in the re- production train and the topic of much misinformation. The accom- panying paper, originally read be- fore the S.M.P.E., reflects the opin- ion of an acknowledged authority on optics on a means for improving evenness of screen illumination.
think of it as traveling from the screen toward the light source.
In Fig. 1 two beams of light are shown, one focusing at the center and the other at the corner of the aperture. The one that focuses at the center of the film aperture fills the front of the projection lens, but the oblique beam does not. Any light belonging to the latter beam that falls on the front lens higher than the upper ray shown will be stopped by the mounting of the rear lens. In a few cases there may be none of this vignetting of the oblique beams, but it is generally found in lenses of any considerable length.
This reduction in the effective aper- ture of the lens for oblique beams re- sults in a reduction of brightness at the margin as compared with the center, even if the source of light were ideal, as here assumed.
Unfortunately, no source of light even remotely approaches such conditions. Available sources that are bright enough are not only tremendously hot, but are also too small, so the science of optics is called upon to make the available sources of light serve our purpose. To get away from the danger due to heat,
:
it is obvious that it is necessary to move the source of light farther from the film. To overcome the difficulty due to the insufficient size of sources the well- known optical law is applied; stating, that by means of a collective element, such as a condenser lens or a concave mirror, a source of light can be made to behave as though it were of any de- sired size, without any more than a minor reduction in its intensity.
With a given light collector, the maxi- mum size the source may be made to appear is the diameter of the collector (condenser lens or mirror) . In practice it is not always possible to make the light source appear as large as desired because practical considerations limit the size of the light-collector.
The laws of optics set a definite limit to the size attainable in condensers and mirrors of a given focal length; and, generally, the laws of economic limita- tions become effective before the optical limitations do. Larger condensers and mirrors could be made and some im- provement in illumination achieved thereby, but the cost would become pro- hibitive.
Since light collectors can not be made as large as they should be made, cer- tain undesirable consequences follow, which will now be examined briefly. There are two cases. The simplier one is presented by customary practice in reflector arcs and will be considered first. Fig. 2 represents an assembly of a 5-inch projection lens of the Cinephor type, a standard aperture, an arc with an 11-mm. positive carbon, and an elliptical mirror 11.5 inches in diameter. The arc is imaged in the plane of the film or very near it. To study this case it is helpful again to consider the light
Right: FIGURE 2
PROJECTION LENS
FIGURE 1
APERTURE LIGHT
SOURCE
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January 1935
INTERNATIONAL PROJECTIONIST
19
as proceeding from the screen to the arc.
Fig. 2a shows the heam of light in- volved in imaging the center of the pic- ture and Fig. 26 an oblique beam that images a point at the corner of the picture. For the center of the picture the mirror is large enough to fill an area of the lens corresponding to a relative aperture of about f/2.8. A beam of light of that diameter entering the lens would focus at the center of the film aperture, diverge from the focal point, and just fill the mirror. Since film aperture and arc crater are con- jugate foci, the beam after reflection by the mirror would come to a focus again at the center of the crater.
Action of Light Rays
The oblique pencil of light is indi- cated by three rays, 1, 2, 3, which divide the beam into two zones. Kay 2 is a limiting ray, the position of which is found by joining the upper edge of the mirror to the corner of the film aperture. Ray 1 is another limiting ray, the highest ray that will pass through the projec- tion lens at that angle. The two rays, and any that lie between them, will participate in imaging the corner of the aperture upon the screen, but they do not include the whole lens aperture. Rays between 2 and 3 are unavailable because the mirror is too small. The obhque beam is limited on one side by the size of the mirror and on the other by the construction of the pro- jection lens. It is smaller than the central beam, and the illumination at the edge of the screen is correspondingly less than at the center.
It should be noted that an additional complication is introduced by the obstruction of light by the carbons and carbon-holder. As a consequence, both central and oblique beams have irregu- larly-shaped holes in the center. The obstruction is slightly greater for oblique than for central beams. The difference is not great from the absolute stand- point, but inasmuch as the oblique beam is of smaller cross-section than the cen- tral one, the relative reduction is con- siderably greater in the former.
If, as in this case, the arc is imaged at the film, the question of arc size is easily settled. If the image of the arc fills the aperture, it is large enough: otherwise it is not, and the margin of the picture will receive no direct illumination.
The question of arc size is not so easily disposed of in the next case, how- ever, which is typical of all condenser combinations. Because of insufficient magnification, the source can not be imaged in the plane of the aperture but must be imaged at some distance ahead of it in order to get light to the margin of the picture, making the geometrical
optics somewhat more complicated than in the case of the reflector arc.
Illumination in the center of the field may be limited either by the size of the condenser or by the size of the light source; according to adjustment it will be one or the other, but not both. In the margin of the field both size of condenser and size of source are likely to be limiting factors.
The conditions are brought out in Fig. 3, which shows the combination of a 5-inch Super-Cinephor projection lens, the most efficient condenser system in common use, 6 inches in diameter, and a 13.6-mm. high-intensity carbon arc as source.
Fig. 3a shows the beam of light con- cerned in imaging the center of the field. Fig. 36 that concerned in imaging the corner of the picture. The drawings are made to scale. The lens has a relative aperture of //2.3; the condenser, with reference to the center of the film aperture, of //2.37. The condenser is, therefore, large enough practically to fill the aperture of the projection lens for the central point of the image.
If we trace the rays limiting a beam of //2.37 through the system, they fail completely to strike the crater of the arc, proving that the crater of the 13.6- mm. carbon is not large enough to utilize the full aperture of the projec- tion lens. If we seek the location of the rays that just strike the edge of the crater of the arc, we find that they occupy the positions marked B, B, and that the beam of light they enclose cor- responds to a relative aperture of //4.8 in the plane of the drawing and //6.7 in a plane at right angles to the drawing, the difference being due to the fact that the back lens of the condenser is a cylinder.
Actual Light Source
It would seem from the drawing that all that would be required to utilize the aperture of f/2.37 would be to pull the arc back from the condenser to the point where the limiting rays A, A in- tersect. This is true, but it would leave the margin of the picture with little or no illumination. The position chosen for the arc is the result of a compromise between central and marginal illumina- tion.
To digress a moment, the dimensions
of the actual source of light in the case of the high-intensity arc are rather in- definite. The diameter of the hottest central area for the 13.6-mm. carbon is 8 millimeters, as nearly as can be measured. This is surrounded by a ring about 2.2 millimeters wide which must also contribute considerable light, but is by no means as bright as the central area. The relative apertures just mentioned are computed for the central 8-mm. area from which most of the light emanates; but the figures do not repre- sent the complete story, because zones of the lens not active according to this analysis actually do transmit light to the screen from the ring of carbon sur- rounding the central gas-ball.
As experiment supports the conclu- sions drawn from a study of the prob- lem in which the 8-mm. central area was regarded as the sole source of light, we can feel fairly safe in ignoring such light as is contributed by the outer ring of the crater.
Referring again to Fig. 3b, four rays are shown. Ray 1 is the highest ray that can pass through the projection lens and arrive at the corner of the aperture. Continued through the con- denser we find that it will not strike the crater of the arc; therefore it can not exist in actual projection.
Ray 2, after being refracted through the lens and passing the corner of the aperture, is refracted by the condenser to the lower edge of the crater. The use- ful area of the lens on the lower side is limited by the size of the crater. Ray 3 is determined by a line joining the corner of the aperture with the edge of the free aperture of the con- denser. After refraction by the con- denser it strikes the arc, and therefore it exists in actual projection.
Any ray lower than 3, such as ray 4, fails to strike the condenser; therefore ray 3 limits the useful area of the lens on the lower side and ray 3 is deter- mined by the size of the condenser. The zone between rays 1 and 2 is useless because the light source is not large enough, and the zone between rays 3 and 4 because the condenser is not large enough.
This setting of the arc-to-condenser distance is found, however, to be about the best compromise between the de- sire for maximum illumination and even
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INTERNATIONAL PROJECTIONIST
illumination. Such an adjustment will afford an illumination at the edge of the picture of approximately two-thirds that at the center. By pulling the arc back somewhat, the brightness at the center can be increased, but the bright- ness at the margin of the picture will suffer.
The ratio of the useful areas of the lens for central and marginal image points, is found, for this adjustment, to be practically the same regardless of the type of projection lens, at least for projection lenses as different in form as the Super-Cinephor, the Cinephor, and the type consisting of two widely separated cemented doublets.
It is practically inevitable under the conditions thus set forth that the illumination should be brighter at the center of the picture than at the edge. By suitable adjustment it is sometimes possible to approach equality of illumi- nation over the whole screen area, but only by sacrificing in total illumination.
Unevenness of illumination has been especially troublesome in projection from behind a translucent screen, where the center of the picture usually appears so much brighter than the edge that the question promptly arises as to whether something can be done about it in the projector. Usually nothing can. The effect is almost entirely due to the char- acter of the space distribution of light transmitted through the screen. With a screen that is a perfect diffuser no serious trouble would exist, but a per- fectly diffusing screen would transmit so little light in any one direction that the image would appear too dark to be satisfactory.
Aperture Lens Suggested One of the suggestions that have been made is to place a collective lens close to the film. Such lenses have been called aperture lenses. In so far as any effect on illumination is concerned, they might be placed ahead or behind the film with equal effect; but since, if placed ahead of the film, they would become essentially a part of the projec- tion lens and have a bad effect upon the image quality, it is impracticable to place them there.
Fig. 4 shows the application of a lens of this kind to the optical system shown
in Fig. 2. Two interesting results fol- low. In the first place, the angular aperture of the beam of light converg- ing to the central point of the film aperture is increased, with the result that a greater area of the projection lens is used and there will be more light at the center of the screen. This is shown in Fig. 4a.
This result is misleading, for it is accompanied by a reduction in the size of the image of the arc formed by the combined reflector and condenser. If that image were originally of just suffi- cient size to cover the aperture it would no longer cover it, and the distance from the mirror to the aperture would have to be increased to restore the arc image to the necessary size. The gain in illumination apparently attained would be lost by the readjustment. If the arc image were originally larger than neces- sary, the same gain in illumination might have been attained without the aperture lens, by decreasing the distance from the mirror to the aperture and re- focusing the arc, thus reducing the size of the arc image and increasing the angle of convergence of the beam of light.
These effects are exactly compensatory, and the conclusion is that no gain in illumination at the center of the field is to be achieved by means of an aperture lens that could not have been attained by a different adjustment of the distances from arc to reflector and reflector to aperture. Since the neces- sary degree of freedom of adjustment may not be present in a given lamp, however, it would not be safe, in any particular case, to conclude that an aperture lens would not provide in- creased illumination.
One Undeniable Advantage A comparison of Figs. 2b and 4b, how- ever, discloses an undeniable advantage in the use of the aperture lens. Whereas without the aperture lens the oblique beam, because of its inclination to the axis, in part fails to strike the reflector and in part fails to utilize other areas of the mirror, the addition of an aperture lens of approximate power will deviate the entire beam, causing ray 4 (Fig. 2b) to strike the mirror and lowering the point of incidence of ray 1.
In fact, the whole area of the mirror
January 1935
may be made to contribute to the for- mation of the image of a point in the margin of the field; leading, therefore, to a level of illumination at the edge more nearly equal to that at the center. In addition to that effect, which is in- evitable, there may be in some cases an increase in illumination at the edge of the field of the same nature as that described above as possible for the center of the field.
Actual tests with an ll^-inch ellipti- cal reflector, and 11-mm. carbon at 70 amps., and a 5-inch Super-Cinephor pro- jection lens led to an increase in aver- age brightness over the entire area of the screen of 25 per cent.
On the other hand, the condition rep- resented in Fig. 3 can not be improved by the addition of an aperture, lens. By examining Fig. 3 it can be seen at a glance that a collective lens placed immediately back of the aperture could indeed change the direction of ray 4 and all other rays between 3 and 4 suffi- ciently to cause them to strike the con- denser, whereas they now miss it com- pletely. The gain, however, is offset by the fact that ray 2, which is now a limiting ray of the active beam, deter- mined by the fact that it is the highest ray that will actually strike the crater of the arc, will not meet the arc if an aperture lens be introduced.
The highest ray that will strike the arc will be lower than ray 2, and what is gained by an apparent widening of the useful beam on the lower side is compensated by a loss on the upper side. The only change is that we shall now be using a different area of the lens for imaging the corner of the pic- ture.
The essential difference between the two typical cases is that in the first case the only limitation of the size of the beam of light, both at the center and at the margin of the picture, is im- posed by the size of the light collector. In the second case, both the light col- lector and the light source are too small for the conditions under which they are used.
In the former case an aperture lens improves evenness of illumination, and in case the light source is large enough it can increase the illumination over the whole picture more economically than by increasing the diameter of the reflector. In the second case, the intro- duction of an aperture lens does not appear profitable from theoretical con- siderations, a conculsion which is sup- ported by experimental observations.
ONE WAY OF DOING IT
Leo Amato, projectionist at the Strand in Wallace, Idaho, was severely burned when he grabbed a reel of blazing film and hurled it through a window.
^
e
Vol. 8, No. 1
EDITORIAL PAGE
JANUARY 1935
This 'Extended'
Service
by Electrics
There is no point in grabbing a baseball bat as a means of resis- tance to the electrics' extended theatre servicing plan. The right of the electrics to engage in servicing operations, upon whatever scale they choose, is as indis- putable as the right of projectionists to band into Unions and offer projection manpower. It is just too bad that the interests of electrics and projectionists happen to con- flict in this particular instance. If projectionists choose to stand aside and make way for an extension of servicing work by the electrics, that is strictly their decision to make - — not ours. Of course, it is to be hoped that Labor will take the consequences of such a decision with the same grace manifested now in stepping aside.
There have been serious abuses in sound system servicing to date in this field. Beginning in 1928 the electrics socked this business for every nickel they could squeeze out of it, and their antics with respect to ten- year contracts, patent hooey, weekly charges, the forced sale of parts, a goodly portion of which were absolutely unnecessary, and general all-around pig-headedness in matters concerning the general welfare of the industry are items for careful cataloging. Not to mention incredible compound interest manipulations, a stiff-backed resistance to change in design of equipments in conformity with progress in the art, and a studied policy of concealing the truth in sound equipment matters of interest to the in- dustry at large.
Fairness demands that an exception to the foregoing be filed in behalf of RCA. This company represents one of the most beneficial influences in this industry since the introduction of sound pictures. Fair in all its industry dealings, whether to exhibitors in the matter of equipment sales and service or to Labor and the press in matters directly affecting either or both groups, RCA has earned special consideration in this field. Labor in particular has had no better friend in this business than RCA.
Further, RCA never attempted to "hog" industry activities in either exhibition or production. Its technical progress is noteworthy: it was the first to introduce all- A. C. operated equipments; it was the first to openly advocate the junking of cumbersome storage batteries, while others clung tenanciously to their use and resented any implication that batteries were less than perfect power- ing devices; it was first in the matter of outright sale of equipments, as well as the first to abolish compulsory servicing, and it has consistently worked toward simplifica- tion and improvement of its equipment. In addition, RCA recording has constantly improved and today it is superb.
Even now, in the face of some rather hard knocks emanating from these columns, RCA has, in refreshing contrast to other companies, come forward and given frank and honest expression to its policy of extended servicing operations. This out-in-the-open action is just another indication of the liberal RCA policy in this field.
RCA's statement of position relative to extended theatre servicing work, as outlined elsewhere in this issue, includ- ing its attitude toward exhibitors, supply dealers, manu- facturers and Labor, is accepted by this publication at its face value. In fact, the experience of this publication with RCA, its contact with RCA representatives, impels the statement that this publication will accept RCA's word for anything; and it recommends that its readers do likewise not only on this question of servicing but in all matters. RCA's record in this field demands nothing less.
The only way in which the electrics can avoid the con- sequence of bitter opposition to their extended servicing plans is to concede the rights of all interested parties. A policy of silence and the attempt to so misuse words as to cloak their real intentions will be fatal to the orderly development of the electrics' plans. Labor has a vital interest in the ultimate effect of any extension of servicing operations by the electrics. Labor should have awakened long ago to the menace to its security of sound servicing by the electrics. Manufacturers can shape their courses as they please, due consideration having been given to the policy of the electrics to date in adopting as "standard" one certain type of equipment and then forcing it into theatres by right of sale and servicing contracts, to the exclusion of all other makes.
Supply dealers have already arched their backs and announce a fight to the end with the electrics. It seems a bit naive to suppose that the electrics, once their ex- tended servicing plan is in operation, would be content to merely "recommend" certain types of equipment and thus pass up an opportunity for substantial additional income in the form of discounts.
It is to be doubted that exhibitors, many of whom have been but recently freed from the electrics' clutches through the expiration of service contracts, will now turn about and again invite the electrics to participate on any broad scale in the operation of their theatres. Some theatre groups, by reason of heavy indebtedness to the electrics, have practically no choice in the matter, of course, yet it should be remembered that the success of the electrics' plans depends not on chain contracts but on signing the thousands of independent theatres in this country, esti- mated to approximate 81% of the total.
Then, too, it might be bad medicine for the electrics if their activities in the sound picture field today are brought to the attention of the Government, which will embark shortly upon an exhaustive investigation of com- munication companies. Not only bad medicine; it might well turn out to be deadly poison.
International Projectionist is, of course, unquali- fiedly and unalterably opposed to any extension of servic- ing operations by the electrics, without exception. It recommends unrelenting opposition by its readers to any (Continued on next page)
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INTERNATIONAL PROJECTIONIST
January 1935
NEW VISTAS IN SOUND TRANSMISSION
Leopold Stokowski
CONDUCTOR, PHILADELPHIA SYMPHONY ORCHESTRA
Rated by many as the world's foremost conductor, Leopold Stokowski evidences herein his keen insight into the technical requisites of good sound transmission, the result of participating in extended tech- nical tests for several years novo. Appear- ing in "The Atlantic Monthly" (Jan., 1935, Vol. 155 No. 1), this article appeared mightily to this writer, whose unshakable conviction it is that projectionists are keenly interested in the allied arts as a means of broadening one's perspective uf the whole field of sound transmission. To be presented in installments, of which this is the first. — Editor.
IS THERE any difference between list- ening to music directly and by radio? I have tried to meet this question in two ways: first, personally and subjectively, as one who has devoted all his life from childhood to making music and trying to understand its true inner nature; and, secondly, objectively, impersonally, try- ing to find the facts as registered, not by ear, but by instruments of precision.
When we listen to music directly the factors involved are complex, but they can be grouped into three classes: (1) the sound source — singer, violinist, orch- estra; (2) the conveying medium, the air between the sound source and our ears; (3) the receiving medium — our ears, which receive the music or vibrations and
pass them to those centres in our brain which transform them into states of be- ing and feeling.
Now what happens when we listen to broadcast music? Obviously (1) the sound source and (3) the receiving med- ium remain the same. But (2) the con- veying medium is only similar in the space between the loud speaker and our ears. Before that is reached many new factors enter. Again these factors are complex, but they can be classed in three groups: —
Three Important Factors
(A) Pick-up. This includes the vary- ing characters and patterns of the sound waves created by the instruments or voices in an empty or full hall, or in a small or large studio, modified by the kind of reflecting or absorbent surfaces formed by the walls, ceiling, floors, and whatever persons or objects there are in the enclosed air-volume. Other variants are the type of microphone used, its de- gree of responsiveness to various zones of the total audible frequency range, the number of microphones, and the rela- tion in space of all the instruments and voices to each other and to all the micro- phones in operation.
(B) Transmission. This is a very complex process that presents problems for which no one as yet has a complete answer. But one element — amplification — can be understood by every music lover. It resembles in some ways the enlarging of a photograph. If we were to take a negative, and enlarge some parts slightly, other parts to twice their original size, others to four times the size, the result would be a distortion, interesting perhaps to those who enjoy the fantastic, but not a true reproduction of the original picture on a larger scale.
In the transmission of music, amplifica- tion is necessary, but if the amplification is greater in some zones of the whole frequency range involved, certain tones or groups of tones sound relatively louder than others, the harmonies become unbalanced, certain individual notes in a melody stand out suddenly in too great relief, important harmonics or overtones are too weak or too strong, the tone-color or timbre of the instruments or voices is changed and degraded, and the whole tonal mass is thrown into a chaotic state of distortion. The result becomes a caricature, and discriminating music lovers will prefer not to hear in a de- graded form music they know and love; and those who hear the music for the first time can have no conception of its true beauty, or of the inspired message it conveys.
To keep the picture simple I have spoken here only of the distortion brought into music by amplifiers; this is (Continued on page 27)
hiditoriCLl (Continued from page 21)
such plan. It advocates the assumption of all theatre servicing work, of whatever character, by projectionists. To the sub rosa charge that projectionists don't know a Hell of a lot about sound system servicing we reply that the electrics at present know a Hell of a lot less than do projectionists about projection equipment, the electrics today being in much the same position with respect to projection that the projectionists were in in 1927-28-29 relative to sound equipment.
Projectionist organizations throughout the country num- ber among their members ample manpower well qualified to do just as good a sound servicing job as the best men possible of muster by the electrics. This publication urges immediate action — and it means immediate action — by projectionist organizations everywhere to obtain servicing work. Failing to take such action, projectionist organiza- tions might just as well lock up their headquarters and throw the key away, for they will be washed right out of the picture by the tidal wave of electrics' domination.
Wage Scales on a National Basis
The only justification for the appearance herein of news and comments pertaining to projectionist wage scales is the fact that somehow or other wage scales seem to
be inextricably tied in with the quality of projection work rendered. Low scales invariably mean a lack of interest in and inattention to one's job. This is freely admitted by all reasonable persons.
There is another angle to this scale question. Projec- tionists in, let us say, California seem strangely apathetic to the wage scale fortunes of their craftsmen in, let us say, Connecticut. Why? we ask. Don't the California fellows, for example, know that wage scales in Connecticut ultimately affect their own scales? It isn't so, do we hear somebody say? Let's see.
Two recent trade press items are served up in support of our contention. First, a theatre concern in St. Joseph, Mo., demands as the basis of settlement of a controversy with an I. A. unit the reversion to one-man shifts — point- ing out that many other I. A. units have granted such a concession, and even going so far as to name specific thea- tres in specific towns.
Second, during the recent Chicago wage scale negotia- tions the exhibitors demanded an agreement embodying a basic hourly rate for a theatre of certain seating capacity and charging a certain admission price. The Chicago ex- hibitors pointed to the recently published tentative wage scale agreement promulgated by the NRA Fact-Finding Committee for New York City.
Got enough? Or shall we go on?
January 1935
INTERNATIONAL PROJECTIONIST
23
ITS work concluded, the Fact-Finding Committee appointed by the NRA to investigate the matter of New York City projectionist scales has released for pub- lication, through the NRA, the tentative scale schedules arrived at after months of consideration by the Committee, com- posed of theatre owners and managers, I. A. officials and NRA representatives. As is well known, the I. A. is now direct- ing Local 306, N. Y. unit of the Alliance. The proposed scales, published on this page, will be the topic of an open hear- ing to be held in Washington on Febru- ary 1, the date now set after three post- ponements. The rank and file of Local 306 is reported ready to offer vigorous objection to the projected agreement, claiming that they were not represented in the negotiations. The General Office of the I. A. is understood, however, to be planning a meeting of Local 305 prior to the Washington hearing.
Many Important Provisions
The Committee schedule is important in many respects. First, the scales per hour are based upon seating capacity and admission price, it being possible, naturally, for the latter to change as many as three times a day for a. m., p. m. and after-dinner performances. The scale probably reflects the top price charged by a theatre during the day.
Second, there is a limitation of hours to 30 per week per man. Third, the minimum rate for any theatre (total theatre cost) is set at $60 weekly. Many independent theatres in New York are now paying a total of only $35 weekly, and have been with impunity since the code became effective.
Fourth, the proposition involves a ten- year contract between Labor and the theatre owners, with the first revision limited to not sooner than two years
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NEWS
NOTES
•
after the scale becomes effective. (This has long been a pet project of N. Y. theatre owners.) Naturally, such re- vision would follow the arbitration route, as provided in the agreement.
Fifth, in anticipation of stiff cuts, a limitation of 33 1/3% is placed upon the extent of any reduction in scale. Editor Kann of Motion Picture Daily estimates the annual savings to circuit operators will be $580,000, split as fol- lows: Loew's, $312,000; RKO, $218,400; and Skouras, $52,000. Broken down, these figures mean a weekly saving to Loew's of $6,000; to RKO of $4,200, and to Skouras of $1,000.
It is understood unofficially that I. A. acceptance of the scales is predicted upon the ability of the theatre owners to deliver New York City af a 100% Union town. At present there are three N. Y. unions: Local 306, I. A. unit; Empire, the first love of the exhibitors in their fight on L. 306 but which in 1933-34 was very friendly to L. 306; and finally, the Allied Union, con- clusively proven as having been formed by the exhibitors with their money just
Proposed New York City Projection Scales
ADMISSION PRICES SEATING 25c 40c
CAPACITY and under 30c 35c and over
400— 599 $.75 $.85 $.90 $1.00
600—799 1.00 1.10 1.15 1.25
800— 999 1.25 1.35 1.40 1.50
1,000—1,199 1.50 1.60 1.65 1.75
1,200—1,399 1.75 1.85 1.90 2.00
1,400—1,599 2.00 2.10 2.15 2.25
1,600—1,799 2.25 2.35 2.40 2.50
1,800—1,999 2.50 2.60 2.65 2.75
2,000—2,199 2.75 2.85 2.90 3.00
2,200—2,399 3.00 3.10 3.15 3.25
2,400—2,599 3.25 3.35 3.40 3.50
2,600—2,799 3.50 3.60 3.65 3.75
2,800—2,999 3.75 3.85 3.90 4.00
3,000—3,199 4.00 4.10 4.15 4.25
3,200—3,399 4.25 4.35 4.40 4.50
3,400—3,599 4.50 4.60 4.65 4.75
3,600—3,799 4.75 4.85 4.90 5.00
3,800—3,999 5.00 5.10 5.15 5.25
Over 4.000— $6.00 an hour.
(aj The figures shown are the rate per hour that the theatre is in operation. No operator shall work more than 30 hours per week.
(b) Where booth cost October 1st, 1934, is less than $60.00 per booth per week, the minimum booth cost shall be $60.00 per week.
(c) Exceptions may be made by an arbitrator or arbitration board, be provided for collectively.
(d) Where booth cost October 1st, 1934, is reduced, no reduction shall be greater than 33 1/3 per cent per week.
(e) The proposed schedule shall exist for a period of 10 years subject to col- lective revision at stated intervals, the first revision to be not sooner than 2 years from the date of enactment.
prior to the NRA and which was ad judged a "company union" by the N. Y. State Supreme Court.
Future of Dual Unions
Nothing definite is known about the future of Empire and Allied should the tentative scale be adopted, and should I. A. succeed in forcing delivery of a 100% Union town. Local 306 at present has 1800 members; Empire has about 500, and Allied 100, a total of 2400 men. Well-informed opinion holds to the view that, on the basis of two-men shifts, New York City can offer at most 1800 pro- jection jobs. The question arises, in the event of consolidation into one large I. A. unit, what is to be done about the other 600 men? The answer obviously lies in the proposal for a 30-hour weekly maximum per man. Nobody is ap- parently even thinking about the possi- bilities of one-man shifts.
On this basis a theatre of 1,000 seats in the highest admission class (40c and more) would pay a total of $1.75 per hour for projection. Assuming a two- men shift, each man would receive 87Y2C per hour; and being limited to 30 hours weekly, he would receive $26.25 for a weekly wage. The smaller exhibitors are protesting vigorously against even this scale.
Dubinsky Row Ended
The long-standing row between Dubin- sky Bros. Theatres and the I. A. unit in St. Joseph, Mo., has ended, with the theatres replacing non-affiliated workers with I. A. projectionists. The former threaten to appeal to the Regional Labor Board, charging that they are being dis- criminated against under NRA pro- visions.
The crux of the bitter battle, raging since last Fall, was the Union's demand for two-men shifts, with the Dubinskys in reply pointing to one-man terms granted by Local Unions in other cities. Kansas City projectionists, who also locked horns with the Dubinskys, are working under terms of an arbitration decision, the nature of which appeals not at all to the K. C. men but which, under NRA procedure, is final.
Code Authority Expense
The Code Authority for the picture business spent $204,166 during 1934. The C. A. main office in N. Y. cost $80,- 720, the Hollywood office was $17,617, while the local boards cost $105,827. Producers and distributors paid $125,- 620, and exhibitors $114,560, during the year. Cash on hand Dec. 31 last was $36,293.
Chicago Scale Talks
Chicago scale negotiations are now proceeding. Union reported to be ask- ing for 20% increase, the theatres countering with request for duplication of tentative New York City arrangement where basic hourly rate is based on seat- ing capacity and admission price.
No trouble in reaching a mutually satisfactory agreement is anticipated.
24
INTERNATIONAL PROJECTIONIST
January 1935
NEW EQUIPMENT
A summary of the latest developments and improvements in the projection field
PROJECTOR carbons constitute one of the most important expense items in the theatre — an expense, incidentally, to which no valid objection can be made, provided the full length of carbon sup- plied by the manufacturer could be util- ized. And therein hangs a tab? — a story, that is, and not the tail end of the car- bon which will be discussed herein.
Substantial economies in carbon costs are possible through the use of a carbon saver, several of which have been mar- keted to date but none of which has proved satisfactory, due either to faulty design or difficulty in handling. Exces- sive carbon costs still is an acute prob- lem, however, and one that merits the wholehearted cooperation of the field.
At present the limitations of the pro- jection equipment make it necessary to discard carbon stubs of at least 4 inches in length. However, projectionists are unwilling to assume the risk of running so closely to the minimum stub, thus very often the discarded stubs run to 6 inches and even more. This results in great waste and excessive costs.
No Drilling, Reaming, Threading
There has been made available recent- ly a carbon saver of new design and utilizing a new principle which, after extensive tests under actual operating conditions, can be recommended as en- tirely practical and capable of overcom- ing all previous objections to such de- vices. This new Saver, for use with 7 mm. Suprex carbons and also with the 9 mm. high-intensity carbons, is unlike all previous similar devices in that it requires no drilling, no reaming or threading of carbons, all of which in- volve a degree of wear and consequent replacement of parts, in addition to con- siderable trouble in handling.
The Saver, detailed in the accompany- ing drawing, is handled as follows: A hollow wooden handle is provided into which is dropped a metal cap, used on each carbon. The unburned end of the carbon stub is inserted into the handle and held against the cap. The entire assembly is then inverted, and the end of the carbon is struck sharply against a solid object to force the cap onto the carbon.
The capped carbon is then removed from the handle and is secured in a metal extension holder by means of a knurled thumb screw. It is then ready for use. The complete operation re- quires only a few seconds, and creates no dust or dirt. It demands of the pro- jectionist a very minimum of effort. The method of attaching the cap to the car- bon and setting up in the extension hold-
er assures a perfect alignment of carbons. A further advantage is that the same end of the carbon is burned throughout, mak- ing it unnecessary to form a new crater in the carbon.
Tests show that it is safe to burn the stubs to within an inch of the metal cap, compared with the stub of six inches or more now being discarded.
The savings possible with this new carbon saver are impressive: With the 9 mm. carbon there is realized a saving of at least 3% inches of carbon, or an additional burning time of 21 minutes. At prevailing carbon prices, the expense of the 9 mm. carbon is reduced from 15 to 12 cents per hour of operation. (This computation allows for the cost of the metal cap used on each carbon.) Savings on the Suprex carbons are corre- spondingly high.
Additional savings may be realized by having the projectionist check the
burning rate of the carbons, at correct current level, and making a note of the consumption in a definite period of time. This will enable him to know the exact length of carbon stub required for each of the reels, according to their running time. The projectionist should also make a note of the time required for the arc to become stable after striking. The second arc should not be struck, naturally, be- fore necessary, the time being based on the foregoing estimate.
This Saver is manufactured by the Pro- jector Improvement Company, Chrysler Building, New York City.
BALDOR ANNOUNCES NEW 25-60 RECTIFIER
THE Baldor Electric Company, of St. Louis, Mo., announces the develop- ment of a 60 ampere rectifier which is specially designed to supply current for the new Suprex carbon arc lamps. Its complete rating is as follows: 25-60 am- peres, 30-40 D. C. volts.
The voltage range of 30 to 40 volts is for the Suprex carbons; while the extra voltage tap of 55 D. C. volts is to supply current to low-intensity carbon arc lamps.
In line with recent recommendations, the "Handy" rectifier will be supplied for operation from a three-phase, 60-cycle A. C. circuit. It cannot be operated from a single-phase circuit.
I
REFLECTOR SHIELDS ENDORSED BY I. P.
VICIOUS and misleading propaganda relative to the worth of the new Reflector Shields introduced recently continues to be disseminated throughout the projection field. Those opposed to the use of the Shields (formerly known as Mir-O-Guards) have "invented" a list of objections to their use, particularly with respect to their alleged "tremendous light loss" and "excessive cost."
Relative to the "tremendous light loss," it should be remembered that
these Shields were subjected to careful tests by members of the Practical Pro- jection Committee of the S. M. P. E., the members of which rank high in pro- jection circles and undoubtedly know more about projection than those who now criticize the Shields ; that the report of the Committee was presented before a crowded convention session and, just prior to its almost unanimous acceptance by the Society, was subjected to a search- ing inquiry by leading lamp manufac- (Continued on second page following)
FIGURE I
Drop Cap (a), then carbon stub (b), in- to capping-tool (c)
FIGURE II
Hold upside down against block of soft wood, and tap lightly on top with hammer
FIGURE III
Remove carbon-stub with cap attached
FIGURE IV
Screw up tightly in holder [d)
B
ne.m
Reamer:/
Detailed Sketch of New Carbon Saver
January 1935
INTERNATIONAL PROJECTIONIST
Reader Interest? Certainly — and
READER LOYALTY, TOO/
Within the last two months L P. circulation (direct paid to the publisher — no agents, no premiums) has increased by 11% — while in the same period advertising in I. P.
has increased by 28%,
I. P. is certainly going places and doing things in the projection field. And why not? I. P. is al- ways first with the latest news of projection technique and equip- ment, always jealously guards high projection standards and vigorously resists any threat to craft welfare.
And I. P. always takes a defi- nite stand on controversial top- ics: in its pages you will never see half-hearted and wishy-washy discussion of vital topics.
That's why I. P. can offer to advertisers more than reader in- terest; that's why it can and does offer reader loyalty, too — an in- dispensable factor in complete acceptance of products adver- tised in I. P.'s pages.
Within the last two months I. P. has been cleaning up the projection field as far as circula- tion is concerned. I. P. circula- tion is unique in that it is en- tirely a direct full-paid cash busi- ness: not a nickel of I. P. sub- scription money goes to agents or for premiums — the only in- dustry paper with this type of voluntary clean-cut circulation. Consider this nice clean, cash circulation within the last two months:
Local Union Amount
Westchester, N. Y 48
Tulsa, Okla 8
Syracuse, N. Y. 45
Long Beach, Calif 36
Rock Island, 111 7
Sioux Falls, S. D 8
Cheyenne, Wyo 9
Sioux City, Iowa 11
Port Arthur, Tex 14
Hamilton, Canada 13
Logansport, Ind 15
Worcester, Mass 47
Cedar Rapids, la 9
Springfield, Mo 10
Jacksonville, Fla 11
San Bernadino, Calif 18
Hartford, Conn 38
Okla. City, Okla 10
Ponca City, Okla 7
Springfield, Mass 22
Bridgeport, Conn 39
Total 425
And these are only the bulk orders direct from organizations, most of them for a two-year
period. Space limitations do not permit reprinting the "raves" for I. P. that accompanied these or- ders. Why, Worcester, Mass., even included some stagehands — if you can tie that one.
There were a host of smaller bulk orders, too, in addition to innumerable individual orders. Even the U. S. Army succumbed to I. P.'s quality appeal and or- dered copies for all its motion picture posts as their first lines of defense.
And so it is that I. P. domin- ates the projection field — in cir- culation and in advertising, or any way you please. Of course, it earned this high position by serving the craft well, by serving up the finest technical articles, by serving up the facts, bereft of hooey, on any controversial topic, and by digging in and fight- ing like Hell when danger threat- ened the art or the craft.
/. P. carries more than jour times the projection
equipment advertising carried by any other industry
publication — naturally.
INTERNATIONAL
580 Fifth Ave.
1
PROJECTIONIST
New York, N. Y.
26
INTERNATIONAL PROJECTIONIST
January 1935
turers, projection specialists and optical men, and that the latter group endorsed the Shield and riddled the "light loss" contention.
Negligible Light Loss
As a matter of fact, the light loss occasioned by these Shields is so small as to be negligible, being less than 1% and impossible to gauge accurately with
the finest of measuring instruments. On the score of "excessive costs," it is apparent that a Shield, costing the theatre less than $4, is a much better proposition than a new mirror, having to be replaced every few months, at a cost ranging anywhere from $8 to $25. The answer to the assertion that mirrors are not replaced "every few months" is that they should be.
PROJECTION RISES TO NEW HEIGHTS IN FIRST AIRPLANE MOVIE SHOW
PROJECTION rose to new heights, so to speak, during the month when for the first time anywhere a motion picture show was given within an air- plane in flight 12,000 feet over New York City. The showing was part of an exploitation stunt in behalf of the new Martin Johnson picture "Baboona," jungle thriller shortly to be released.
The Douglas plane with which Cap- tain Eddie Rickenbacker recently set a new transcontinental transport record was utilized for the stunt, each flight of which saw aboard many distinguished public personages and reporters for the trade and daily newspaper press.
Of particular interest here is the pro- jection equipment installation, the set- up for which is shown in the accompany- ing illustration. A completely all-A. C. operated Simplex Portable Sound, em- ploying a Mazda, was used, together with a rotary converter for the A. C. Ten 12-volt storage batteries supplied the power. The picture was 3x4 feet.
Each flight lasted an hour, with 3 reels being shown each time during the latter portion of each trip. The entire
installation was supervised by Messrs. Herbert Griffin and Henry Heidegger of the International Projector Corp.
"The quality of the picture was sur- prisingly good," said Mr. Griffin. "Orig- inally we planned to climb to 12,000 feet and then, after cutting the motors, glide to a landing, so that the sound would not be affected by the roar of the motors. We estimated that the glide could be stretched out to nearly half an hour, permitting the showing of 3 reels.
"Our first trip changed this plan, how- ever, for we found that the perfectly soundproof cabin permitted excellent re- sults, even with the motors roaring away." (Ed.'s Note: This soundproofing job was done by Sperry-Gyroscope, well known in the picture industry through their arc patents.)
"The picture was fine — really splendid, and so steady and clear that every word of the sound could be heard. Interest- ingly, one point in the picture has a sudden 'pan' where the camera follows a leaping tiger at a sharp angle, and so realistic is the shot that all the pas- sengers on every trip got a sudden im- pression of the plane turning sharply at a 90-degree angle and instinctively grabbed for their seats. Yes, there were
James J. Shaughnessy
JAMES J. SHAUGHNESSY, presi- dent of Local 650, Westchester County, N. Y., died on January 12 when peritonitis set in after an acute attack of appendicitis.
Shaughnessy ("Jim" to his thousands of friends within and without Labor circles), at 36 was one of the youngest Local leaders in the Alliance, having headed Local 650 since its formation in 1927. It isn't necessary to say that Jim Shaughnessy was one of the greatest Labor leaders, nor that West- chester County isn't among the largest cities in America. But it is important to say that Westchester, despite its close proximity to the Labor cesspool that is New York, and having within its borders Union theatres owned by the same people who operated non- union theatres in New York, has al- ways been and still is 100% Union.
This, after all, is the true mark of Jim Shaughnessy's worth — the fact that in his particular job he was a champion. Having nursed Local 650 along since it was only a baby Local, Jim Shaughnessy needs no other monu- ment; the enduring success of "his baby" will mark him apart from others less capable.
And Jim was a man, too — a man's man, as was attested to by the vast congregation of important personages from all walks of life who gathered to pay their last respects. These puny lines could never convey just how much of a man Jim was. It's Hell to have to write them . . . and still there's something swell in harking back to the grand person that was Jim Shaugh- nessy.— J. J. F.
many sheepish expressions on view when they realized their mistake."
Said Martin Johnson in a letter to Mr. Griffin:
"I appreciate tremendously your efforts in helping us to put over last night's unique showing of 'Baboona.' For the first time sound pictures have ever been shown in an airplane, and in the face of many mechanical difficulties, the results surprised me.
"The picture was fine and cleancut, and the steadiness of the image is a tribute to that marvelous Simplex of yours. One could hear every little bird sound; in fact, I think our air show was better than that in the projection room when we were editing the film.
"Your Simplex is so wonderful that I'd like to have everybody know about it."
FIRST AERIAL SOUND MOVIE SHOW
Showing complete sound picture projection installation in tight quarters. Fine
technical results attained in series of flights 12.000 feet over New York City
L. U. 245 ANNUAL BANQUET
Local 245 held its annual banquet on Jan. 6 at the Hotel Edison in Lynn, Mass. Present at the affair, in addition to the membership, were local officials, city and district exhibitor managers, sound com- pany representatives, I. A. officials and a limited number of invited guests.
The principal speaker was James J. Finn, editor of International Projec- tionist, who observed with satisfaction the presence at the affair of managers for the first time and who made a strong plea for closer employer-employee
January 1935
INTERNATIONAL PROJECTIONIST
27
cooperation. Mr. Finn detailed several new technical developments which aid in putting on a better show. He character- ized sound system servicing as "nothing less than a racket" and urged projec- tionists to assume jurisdiction over this type of work.
BARROWS, BURKE RE-ELECTED, FORMER FOR 18th TERM
Thad C. Barrows and James F. Burke were elected president and business rep- resentative, respectively, of Boston Local 182 in a recent election. These two men have served the Local for many years, with Barrows now entering upon his 18th consecutive term. Other officers are: Bernard McGaffigan, vice-president; Al Moulton, financial secretary, and Joe Rosen, treasurer.
Named to the executive board were Maurice Addleson, Louis Pirovano and Joseph Nuzzolo.
NEW VISTAS IN SOUND TRANSMISSION
(Continued from page 22) only one of the elements that can dis- tort in broadcasting.
(C) Receiving equipment. For per- fect reception we should need a loud speaker that would respond with equal sensitivity from about 30 to 13,000 cycles per second. All the receiving sets that do not have such a speaker cannot help distorting the music.
Adequate transmission of music must meet three requirements: it must faith- fully transmit (1) the complete fre- quency range; (2) the complete intens- ity range; and (3) with the true auditory perspective.
The fundamental principles of radio are a mystery that we may never fully understand. The greater the scientist, the more clearly he realizes and the more frankly he tells us how little he knows. As we learn, we become more aware of our ignorance. But radio proc- ess can be outlined in simple terms. If you talk over the radio, the sound of your voice is picked up by a microphone, transformed into electrical energy, amp- lified, carried by wire to a transmitter, sent out into space as radio frequen- cies— or Hertzian waves,— picked up by receiving equipment, transformed into electrical energy, amplified, sent out by the loud speaker as sound or audio-fre- quencies reproducing your voice. Briefly stated, this is the general process for the transmission of either speech or music.
In a parallel sense, but on another plane, we know the circuit that music follows — from inspiration, through trans- mission (composer and interpreter) and reception (music lover), back to inspira- tion. The important question is the de- gree of faithfulness with which sym- phonic and operatic music can be deliv- ered in our homes, and the message con- veyed in its full value.
At present these types of music come
The New
BRENKERT
?rrp*>
High-Intensity Reflector Arc Lamp for D. C. Suprex Carbon Operation
— is proving a revelation in screen results and low operating costs throughout the country
• Wide range feed regulation with separate negative feed adjustment permits operating this lamp at 34 to 65 amperes with positive Suprex carbons of 6-mm., 7-mm., and 8-mm. diameter.
• This is the widest range yet accomplished and permits a proper screen intensity to meet requirements of various size theatres with a range of operating costs to suit your pocketbook.
• Rugged construction and accurate, dependable operation assures complete satisfaction.
A Brenkert product throughout, which means a guarantee of perfect projection
See the Brenkert distributor or write direct for literature to
BRENKERT LIGHT PROJECTION CO.
Engineers and Manufacturers 7348 St. Aubin Ave. Detroit, Mich.
28
INTERNATIONAL PROJECTIONIST
January 1935
SUPER INTENSITY
AUTOMATIC PROJECTION LAMP
H. C. 10
Super Intensity Lamp
The
Lamp With Accurate Arc Regulation
and Arc Focusing by Means of
the Heat From the Arc Itself
H. C. 10 Features:
• Self-Starting • Self-Focusing
• Independent Negative Feed Regulation
• Magnetic Stabilization • Better Arc
• Self -Lubricating Bearings
• Standard Ammeter • Carbon Indicator
• Forced Air Cooling • Correctly Shaped Hood
• No Feed Rollers • Full 22-inch Trim
Descriptive booklet on request. Write for it to
HALL & CONNOLLY, Inc.
24 Vandam St. New York, N. Y.
from the radio in incomplete and changed form. The scientific explanation can be simply stated. The character or quality of tone in music is mainly due to harmonics or overtones. At present, many of these cannot be and are not transmitted and received by radio. The result is that such sounds as the muted trumpet or the oboe cannot be trans- mitted and received faithfully, and there- fore frequently come to us in changed or distorted form.
Harmonics and Timbre
Harmonics or overtones are most eas- ily explained by an example: If you sing a note, you probably hear only that single note, which musicians call the fundamental. Above that, however, is also sounding the octave, usually less loud- And above the octave is sounding another soft tone five notes higher. And another, four notes higher still. And an- other three notes higher still. And so on. These are the overtones or har- monics and they have simple ratios of vibrations or frequencies or cycles to the fundamental tone. To every single vibra- tion of the fundamental tone the first overtone has two vibrations, the second overtone three vibrations, the third over- tone four vibrations, and so on.
The relative loudness of the harmonics to each other and to the fundamental is the cause of the quality or timbre or tone-color of a tone. For example, if the high harmonics are louder than the low harmonics and the fundamental, the tone- color produced will be thin and piercing and reedy, like the oboe or muted trump- et or the gamba or reeds of an organ. But if the low harmonics and the funda- mental are louder than the high har- monics, the resulting tone will be round and full, like a flute, or a horn played softly in the middle register, or the dia- pason of an organ.
Requisite Frequency Range
The adequate transmission of the har- monics in operatic and orchestral music includes frequencies or vibrations as rapid as 13,000 per second. By fre- quency is meant roughly what musicians call "pitch" — whether a tone or group of tones is high or low or in the middle register. For example, if you sit at the piano, the notes immediately in front of you or in the center of the keyboard are in the middle register, those to your right hand in the high register, those to your left hand in the low register. In much the same way, the engineer and physicist speaks of high, middle, and low frequen- cies or periodicities or cycles. He meas: ures them in time so that the "A" to which the violinist tunes his instrument has 440 cycles per second.
These frequencies can be thought of as alternate condensation and rarefaction of air — as a series of pressures. For the purpose of this writing, differences of frequency or pitch can be thought of as the contrasting sounds of the high tones of a flute or violin, as examples of high frequency; the mellow sounds of a cello or the lower sounds of a contralto voice, as examples of middle frequency; and the deep sounds of an organ pedal or of
January 1935
INTERNATIONAL PROJECTIONIST
29
the double bass, as typical low frequen- cies.
Instead of the 13,000 frequencies per second which are necessary for the ade- quate transmission of orchestral music, radio listeners in most of the homes in this country are hearing, at present, up to about 5,000 frequencies or vibrations per second and sometimes fewer. That part of the music which should be conveyed from 5,000 to 13,000 frequencies is obvi- ously lost.
The 13,000 frequencies I have men- tioned is not a figure set arbitrarily. It results from very close and exact tests, which were made by Dr. Harvey Fletcher, head of the Bell Telephone Laboratories and a group of assistants, of which I was one. These tests were made on a mixed
group composed of engineers, musicians, amateurs, and others. Our aim was to see up to what periodicity it was essential to be able to transmit sound in order faithfully to broadcast good music for the average ear. We began, of course, with full realization that the response of ears is infinitely varied.
Ear Response Differs It is not too much to say that every- one's ear response differs at least in some slight degree from that of his neighbor. Some of us hear up to 20,000 frequen- cies per second. Some up to only 12,000. The average capacity is perhaps about 15,000. Our tests convinced us that, for the average ear, up to at least 13,000 is really necessary, and that fewer than that
will not carry orchestral and operatic music with complete faithfulness.
The first step toward making it pos- sible to include the missing vibrations between 5,000 and 13,000 is, in my opin- ion, to widen the channels that were ap- portioned some years ago by the Radio Commission. At present these channels are so narrow that the full frequency range necessary for the complete and un- distorted broadcasting of good music is practically impossible.
Of all the available frequencies for such forms of communication as wireless telegraphy and telephony, distress and other shipping signals, and the radio we know for the sending out of music, lec- tures, speeches, etc., only a part is al- lotted to the radio we use — and this must
NOW AVAILABLE IN ALL SIZES !
REFLECTOR SHIELDS
[Formerly Mir-O-Guards — Patent Pending]
Cut Your Reflector Costs 75% and improve projection
All Sizes Now Ready
|
Type |
Diameter |
Type of Projector |
|
PL |
7s/8 11^ |
Peerless Low |
|
PHL |
Peerless Hi-Low |
|
|
PDC |
14 |
Peerless Magnarc |
|
ADC |
9 |
Ashcraft DC |
|
MDC |
10^4 |
Morelite DC |
|
SL |
8 |
Strong Low |
|
SHL |
12 |
Strong Hi-Low |
|
SDC |
10 |
Strong DC |
|
BHL |
12 |
Brenkert Hi-Low |
|
BDC |
10 |
Brenkert DC |
Stop buying reflectors every few months. Use Reflector Shields— the perfect protector. These Shields are of ciystal clear, heat-resisting glass,
having the identical curvature of, and fitting perfectly over, the reflector.
Reflector Shields keep your reflector always new. No more pitting, no more dirt and grime, no more cracked reflectors — for the Shield pro- tects the mirror and bears the brunt of the constant attacks of pitting and dirt.
The Shield is very inexpensive and permits enormous savings in reflector costs. You can afford to always have these Shields on hand; you can buy them in sets — perfectly suited to your particular type of reflector. Reflector life is prolonged indefinitely with this sensational projection aid. Just slip a Shield in front of your reflector — and then forget it. Months later you need only slip out the Shield and replace it with another. Just one minute and the job is done. And your mirror still is NEW!
Extensive tests prove that these Shields actually aid projection by offering constantly a good reflecting surface. There is no light loss with this Shield; the endorsements of leading projectionists everywhere prove its quality.
Tell your theatre manager or owner today about this sensational new projection aid that cuts reflector costs by 75% and improves projection. If your dealer cannot supply you, write to us direct — today!
Reflector Shields are sold only
through dealers. Inquiries are
invited from reputable dealers
everywhere.
Why spend from $15 to $30 for a new mirror every few months, when by using these Shields you can have perfect projection always for the comparatively inexpensive sum of from $3.95 to $5.50, depending up- on the size of your reflector?
Prominent projectionists
everywhere recommend the
use of Reflector Shields for
efficiency and economy.
REFLECTOR SHIELD CO.
235 Fourth Ave.
New York, N. Y.
30
INTERNATIONAL PROJECTIONIST
January 1935
Cooperation with Labor and Exhibitors
THROUGH INDIVIDUAL OWNERSHIP
Members of the Independent Theatre Supply Dealers Associa- tion cooperate with Labor and ex- hibitors on the basis of individual ownership. The Independent dealer has a vital interest in the welfare of Labor and the progress of the exhibitor, and to these groups he extends the utmost cooperation.
No long-distance servicing plans for Independent dealers, who are local men interested in local wel- fare. They are alive and alert to
your needs at anytime of the day or night. Independent dealers offer the best merchandise obtainable — the product of individually-owned and operated factories.
That is why Independent dealers show a steadily increasing volume of business, and an ever-growing ability to render service — when, as and how you require it. Your con- tinued cooperation with Independ- ent dealers will insure that you get the best merchandise, the highest type of service and fair treatment.
Patronize Independent Supply Dealers Association members
and further the cause of a free and open market for
supplies — and Labor
INDEPENDENT THEATRE SUPPLY DEALERS ASSOCIATION
Executive Offices: Paramount Bldg., New York, N. Y.
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be subdivided so as to give each of the transmission stations of this part of the world a channel that will not interfere with adjacent transmitters. There has been a great demand for these channels, and in order to supply this demand the channels have been made narrow. These narrow channels do not permit the nec- essary frequency range of about 30 to 13,000 cycles per second, but up to only about 5,000.
The first and fundamental need is for Washington to revise its allotment of channels so that they can be broader.
The second step is for transmission stations to send out music with an equal response from about 30 to 13,000 fre- quencies per second. The more progres- sive transmission stations are eager to do this. In thus enlarging the frequency range of transmission of music no harm will be done to the broadcasting of the voice. On the contrary, brilliant voices need high harmonics for complete trans- mission of singing, and even speaking voices need high harmonics for sibilants. Enlarging the frequency range need not interfere with short-wave transmission which gives us a wider radius of effec- tive reception. Short-wave and wider frequency range are two different sub- jects— not necessarily interfering with each other.
Present Sets Inadequate
The third step is for the makers of re- ceiving sets to design sets that can re- ceive and give out to the listener with an equal sensitivity of response from about 30 to 13,000 cycles per second. Some of the makers of receiving sets are only waiting for Washington to enlarge the channels before they too enlarge the re- ceiving range of their sets.
These three steps will involve temp- orary practical difficulties. I am told that, from a commercial point of view, these difficulties are not to be disposed of lightly, but that the farsighted manufac- turer will see that a satisfied and expand- ing radio public is his real objective and is the permanent security of his own commercial interests.
From the standpoint of a musician and radio enthusiast, it seems to me that if music can be broadcast more faithfully by employing the latest scientific discov- eries, and if the net result of employing these is not only raising the quality of musical sound but also increasing the number of eager and appreciative listen- ers from coast to coast, then the changes necessary, and the discarding and re- placing of a considerable amount of pres- ent equipment, can only be regarded as a secondary consideration. In any case radio equipment is wearing out and be- ing replaced all the time, with the situ- ation as it now is.
Technical Difficulties
There are also certain technical diffi- culties, for which there may be more than one solution. In offering my own suggestions as to how these problems can be dealt with, I have well in mind that there is more than one way of doing most things. The ideas I am presenting here
January 1935
INTERNATIONAL PROJECTIONIST
31
will, I hope, invite the attention of physi- cists, radio engineers and the public to the problem of what music needs, and invite consideration not only of my own proposals, but of alternative proposals which experts in various fields have made or may make.
Fewer, Wider Channels
One way of widening the channels might be to zone the country and to apportion wider channels in such a way that the same channel could be used for a number of zones, so spaced out that they would not overlap and interfere. This would mean fewer channels, wider channels, and intelligent organization of the whole country for radio. All this is possible. Each zone using the same wide channel could broadcast a differ- ent program at the same time. Or some or all of the zones using the same chan- nel could broadcast the same program- mes by wiring the stations together. But this wiring system would have to be of high quality. Ordinary telephone wiring systems adequate for speech would not be suitable for music. This kind of zon- ing might mean that transmission sta- tions would have to adjust their power in order to prevent interference between those zones which would be using the same channel. Obviously, there would be, for a time, some inconvenience to the transmission stations in a general re- quirement to readjust their power. The ultimate result, however, would be a gain to all radio listeners, who would, by this revision or some other plan achiev- ing the same result, be able to hear music and speech in complete and undis-
torted and satisfying artistic form. What the musician calls loudness and softness, the physicist calls intensity. He measures intensity by units called deci- bels. Good music needs, in an opera house or concert hall, an intensity range of about 85 decibels. That is to say that,
from the softest sounds of an orchestra or operatic ensemble to the utmost sonor- ities of a great tutti, there is and should be a very wide range or difference.
There are physical, psychological, and musical reasons for this. Much of the emotional effect on us of music and its dy-
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32
INTERNATIONAL PROJECTIONIST
January 1935
A
nnouneing • . .
SPECIAL
ANNIVERSARY
ISSUE
of
INTERNATIONAL PROJECTIONIST
... to be published as a special and separate section of the March issue and mailed free to all I. P. subscribers.
To contain a review of pro- jection progress during the past three years together with a pre- sentation of the best I. P. ar- ticles within the same period. Also, other feature articles.
This special edition will serve admirably for continual ready reference.
Be sure that you get your copy.
To advertisers this special edi- tion has particular appeal be- cause of its permanent reference character.
namic intensity of mood and expression depend on gradual or quick increase of loudness (crescendo) and gradual or quick reduction of loudness (dimin- uendo ) . Also sudden accents on one or more notes, or on a chord, or on a mel- odic outline, either on the top edge, or the lower edge, or somewhere in the mid- dle of the total mass of sound, add at certain moments to the poignancy of the music. Another factor in increasing the eloquence of some kinds of musical ex- pression is the powerful contrast of a great mass of loud harmony followed or preceded by delicate, distant-sounding music.
One of the greatest values of music — its power to evoke in us moods and states of feeling and of being — thus de- pends greatly upon dynamic contrast and gradation. Of course the potential in- tensity range of an orchestra or operatic ensemble varies in different concert halls, opera houses, and radio studios. Some of the influencing factors are the texture of reflecting surfaces, the degree of rigid- ity of the structure to which these sur- face materials are attached, the size and form of the total air-volume that is vi- brating, the rapidity of absorption at various frequency levels, the general rev- erberation period of the enclosed space, and so forth.
For example, the Centre Theatre in Radio City gives — to one conducting in it — the impression of an almost limitless intensity range. Some other halls have
so narrow a potential range that music in them sounds monotonous and rela- tively colorless. Every orchestra varies in intensity range, and even the same orchestra varies with different conductors, for psychological reasons which I am far from fully understanding.
Today in broadcasting a symphony orchestra, we are employing an intensity range of about 30 decibels, instead of the 85 decibels that we are using in our concert playing in performing, for in- stance, music with the immense dynamic range of Wagner. In broadcasting, the 85 decibels have to be compressed to about 30, and this is usually done by the engineer at the controls.
The control engineer has certain instru- ments before him, one of which is like the volume control on your radio set. By turning it one way he gives the music the full intensity that is the result of amplification. By turning it progres- sively in the opposite direction he gradu- ally attenuates or softens the sound of the music. By reducing the loud moments and by increasing the soft parts he compresses the intensity range so that there will be no overloading by loud music and so that the soft music will be easily audible and not covered by the "noise level," which is the sum of all the extraneous sound produced by the trans- mission and receiving equipment, plus audience noise, if an audience is present, as in a concert.
This audience noise is often greater
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January 1935
INTERNATIONAL PROJECTIONIST
33
than might be imagined. The total sound of several thousand persons turn- ing the pages of the programme book, making other movements, talking or whispering, coughing, the sound of late comers finding their seats, of the opening and closing of doors, is surprisingly high.
The controlling and compressing of the intensity range can also be done by the conductor, who can make the soft pas- sages louder and the loud passages softer, but this devitalizes the music.
For the reception of operatic and sym- phonic music in the average home, a dynamic range of 85 decibles would not be necessary, but music needs a much greater variation of loudness and softness than is at present possible.
Auditory Perspective
When we listen to music in the opera house or concert hall the complex mass of sonority enters our two ears from the front, both directly and by reflection, and from the sides and back by reflection only. Our impression is that the major part of what we hear is direct and the lesser part reflected.
But the truth is the reverse. The re- flected sound in most theatres and halls is very rich and full, and is greater than the directly heard sound. Although we may not be conscious of it, our two ears are hearing slightly different sound-pat- terns because the reflections from right and left are different in time and in the intensity of all the component parts of the complex sound-mass. Unconsciously we compare these different impressions received from right to left and this com- parison gives us the sense of perspective — of a feeling of tonal spaciousness. More of this subject will be included in that part of this writing that deals with "wired transmission."
The microphone is a kind of electric ear. In broadcasting, the microphone picks up the sound which is afterward brought by a complicated process to our ears. But the microphone is a single ear attached to a single circuit or means of carrying the sound to us. To convey music with full and true auditory per-
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spective, we should have, in my opinion, double circuits which could be made to correspond to our method of hearing with two ears and which would give us the tonal spaciousness and beauty of sound that make music so satisfying in a large and well-planned auditorium.
When all the results outlined in (1) Frequency Range, (2) Intensity Range,
(3) Auditory Perspective, are brought about, it will be more possible to find the answers to the two great questions of how the cost of radio can best be met and what ought to be the relation of government to radio. First of all we must see clearly what we need from radio socially and technically. (To be Continued)
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34
INTERNATIONAL PROJECTIONIST
January 1935
Your Iheatre needs this
TEST REEL
• No longer need you be in doubt about your projection equipment delivering highest possible quality results. These reels, each 500 feet long, are designed to be used as a pre- cision instrument in testing the performance of projectors.
• The visual section includes special targets for detecting travel-ghost, lens aberration, definition, and film weave. The sound section includes recordings of various kinds of music and voice, in addition to constant frequency, constant amplitude recordings for testing the quality of reproduction, the frequency range, the presence of flutter, and 60-cycle or 96-cycle modulation, and the adjustment of the sound track.
• For theatres, review rooms, exchanges, laboratories and wherever quality reproduction is desired. These reels are an S.M.P.E. Standard, prepared under the supervision of the Projection Practice Committee.
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Address:
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33 West 42nd St. New York, N. Y
SOMETHING FOR NOTHING: HOW MUCH WILL IT COST?
(Continued from page 10)
sound and against which so much criticism has been directed.
Outside of making inspection of thea- tres or any department thereof, it will be necessary for the "electrics" to con- tinuously make laboratory tests of vari- ous pieces of equipment and compile data so that the proper recommendations and specifications may be drawn. This will cost considerable money. Where is this money to come from?
The R. & R. Contract
The R & R (repair and replacement) Plan whereby maintenance and service may be had for a fixed charge was only developed after a great deal of opposi-
tion to the previous plan and prices of parts forced a change in policy.
True, the independent dealers do not possess elaborately-equipped research laboratories and do not have the time to play around with high-sounding theory. They merely happen to know the equip- ment and supply business from "A to Z" from a practical standpoint, which can only be acquired by actual experi- ence and contact. They have always given to the exhibitors the kind of serv- ice that is most needed and appreciated in the many emergencies which crop up daily in the operation of the theatre.
Is it not only fair, in that case, but also good business for the exhibitors to give their patronage to these well-trained and helpful members of the trade? Frankly, we believe that it is and that it would be a very good thing for the
projectionist to overlook no opportunity to impress this upon theatre owners.
We must repeat that the most careful thought does not enable us to understand just how "something can be had for nothing." Possibly, our theoretical training has not been adequate to give us the solution to that problem, thus we must conclude that there is dirty weather ahead. That being the case, it is a cer- tainty that the interests of dealers, manu- facturers, exhibitors and Labor are threatened, the interests of these groups being very closely allied.
The dealers know that they cannot compete with the unlimited resources of the powerful combines mentioned here and in Mr. Finn's previous article. Con- sequently, they feel that the fight must be carried along other lines and will not hesitate to invoke the protection of the Government in the knowledge that we still have legislation designed to hold monopolistic activities in check and to suppress any attempts to ban free com- petition through the use of practices in restraint of trade.
Possibly big business, as exemplified by the "electrics," is turning philan- thropic, but then what is the meaning of the following excerpt from a letter from one of our members:
"Recently on a job at E. Millinocket, Maine, we were installing complete equipment, except for sound. We had secured the contract including sound screen which was later cancelled by our customer because erpi has a consider- able number of users of their equip- ment in this territory who are operat- ing under the so-called R & R Plan." To insure the distributors of a uni- form quality and through this source, the buyers, our organization contem- plates establishing test procedure and having all merchandise submitted to a pactical test prior to its sale.
Members of the Association have the facilities for making screen measure- ments, illumination tests and other tests, and are locally in contact with prominent architects and ventilating engineers and others. The class of people whom they contact locally are men of repute and high professional standing in their com- munity. Dealers are more familiar with local problems than any chain service or organization could ever be. While these men may not have the facilities of a great laboratory behind them they are familiar with the business which combined with the practical experience of the individual members is to be con- sidered.
The dealers will go to the limit in their efforts to stay in business and to that end urge the cooperation of all other interested parties — namely, manufac- turers, exhibitors — and Labor.
Something for nothing? How much will it cost?
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EXHIBITORS MUST AWAKE TO THE ULTRAJMPORTANT PART PROJEC* TION IS PLAYING IN THE LIFE OF THEIR THEATRES. They must realize that the paltry few dollars they may succeed in saving on their projection repair bill will * assume unrecognizable proportions as com* pafed to the fallingoff in attendance as regis* tered by the box office report* And they must realize that good projection is no longer a matter of speculation—but a 100% gold-bond investment, with the resultant profits bearing a distinct relation, comparatively, to the origi* nal sum invested*
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Projectionists Extend Servicing Activities
SUPREX OPERATING HINTS . . . ALUMINUM REFLECTORS . . . WHAT ABOUT TELEVISION? .. .THE MOTOR CONTROL UNIT . . . NEWS NOTES
iur» 1935 >l. 8 No. 2
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The best book ever published for the motion picture pro- jectionist. The book contains nearly 1200 pages and over 400 illustrations. Complete instructions covering the care and operation of sound motion picture equipment. All troubles that can happen to your equipment will be found listed in this book with simple instructions for the cause and remedy of same. Thousands of projectionists swear by this book.
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CAMERON PUBLISHING COMPANY, WOODMONT, CONN., U. S. A.
February 1935
INTERNATIONAL PROJECTIONIST
The experience of large down-town theatres with High Intensity projection has proved that patrons appreciate comfortable vision on entering the theatre and clear, snow white projection on the screen. . . . The box office value of these features is now available to theatres of moderate size at little added cost of operation. . . .
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INTERNATIONAL PROJECTIONIST
February 1935
Reader Interest? Certainly — and
READER LOYALTY, TOO/
Within the last two months L P. circulation (direct paid to the publisher — no agents, no premiums) has increased by 11% — while in the same period advertising in I. P.
has increased by 28%.
I. P. is certainly going places and doing things in the projection field. And why not? I. P. is al- ways first with the latest news of projection technique and equip- ment, always jealously guards high projection standards and vigorously resists any threat to craft welfare.
And I. P. always takes a defi- nite stand on controversial top- ics: in its pages you will never find half-hearted and wishy- washy discussion of vital topics.
That's why I. P. can offer to advertisers more than reader in- terest; that's why it can and does offer reader loyalty, too — an in- dispensable factor in complete acceptance of advertised prod- ucts.
Within the last two months I. P. has been cleaning up the projection field as far as circula- tion is concerned. I. P. circula- tion is unique in that it is en- tirely a direct full-paid cash busi- ness: not a nickel of I. P. sub- scription money goes to agents or for premiums — the only in- dustry paper with this type of voluntary clean-cut circulation. Consider this nice clean, cash circulation within the last two months:
Local Union Amount
Westchester, N. Y 48
Tulsa, Okla 8
Syracuse, N. Y 45
Long Beach, Calif 36
Rock Island, 111 7
Sioux Falls, S. D 8
Cheyenne, Wyo 9
Sioux City, Iowa 11
Port Arthur, Tex 14
Hamilton, Canada 13
Logansport, Ind 15
Worcester, Mass 47
Cedar Rapids, la 9
Springfield, Mo 10
Jacksonville, Fla 11
San Bernadino, Calif. . ... 18
Hartford, Conn 38
Okla. City, Okla 10
Ponca City, Okla 7
Springfield, Mass 22
Bridgeport, Conn 39
Total 425
And these are only the bulk orders direct from organizations, most of them for a two-year
period. Space limitations do not permit reprinting the "raves" for I. P. that accompanied these or- ders. Why, Worcester, Mass., even included some stagehands — if you can tie that one!
There were a host of smaller bulk orders, too, in addition to innumerable individual orders. Even the U. S. Army succumbed to I. P.'s quality appeal and or- dered copies for all its motion picture posts as their first lines of defense.
And so it is that I. P. domin- ates the projection field — in cir- culation and in advertising, or any way you please. Of course, it earned this high position by serving the craft well, by serving up the finest technical articles, by serving up the facts, bereft of hooey, on any controversial topic, and by digging in and fight- ing like Hell when danger threat- ened the art or the craft.
/. P. carries more than four times the projection
equipment advertising carried by any other industry
publication .... Naturally.
INTERNATIONAL
580 Fifth Ave.
1
PROJECTIONIST
New York, N. Y.
February 1935
INTERNATIONAL PROJECTIONIST
0JECTI0NIS1
With Which is Combined PROJECTION ENGINEERING Edited by James J. Finn
Volume 8
FEBRUARY 1935
Number 2
Monthly Chat 5
Efficient Operation of the Sup- rex Carbon Arc 7 W. C. Kalb
Step-By-Step Analysis of Sound Reproducing Equipment, VII 10 Aaron Nadell
New Vistas In Sound Trans- mission, II Leopold Stokowski
12
Hints on Efficient Low-Intensity Operation 13
Rolf R. Gruning
S.M.P.E. Head Asks Exhibitor Aid in Improving Theatre Re- production 14
Present Status of Television Is Discussed By Dr. Goldsmith 14
Aluminum Reflecting Surfaces For Projection Work 15
J. D. Edwards
Projectionists Extend Sound System Servicing 17
James J. Finn
I. A. President Browne on Sound System Servicing 17
New Servicing Plan an Old 'Racket' With New Twist 21
J. E. Robin
I. A. Takes Over Local 110 Fol- lowing Slaying of Maloy 21
News Notes Technical Hints Miscellaneous Items
Published Monthly by
FINN PUBLISHING CORPORATION
JAMES J.
580 FIFTH AVENUE, NEW YORK, N. Y. Circulation Manager, Ruth Entracht
Subscription Representatives
Australia: McGills, 183 Elizabeth St., Melbourne New Zealand: Te Aro Book Depot, Ltd., 64 Courtenay Place Wellington England and Dominions: Wm. Dawson & Sons, Ltd., Pilgrim St., London, E. C. 4.
Yearly Subscription: United
States and possessions, $2 (two years, $3) ; Canada and foreign countries, $2.50. Single copies. 25 cents. Changes of address should be submitted two weeks in advance of publication date to insure receipt of current issue. Entered as second-class matter
February 8, 1932, at the Post Office at New York, N. Y. under the act of March 3, 1879. Contents copyrighted 1935 by James J. Finn Publishing Corp. International Projectionist is not responsible for personal opinions appearing in signed articles in its columns.
MONTHLY CHAT
WE RATHER fancied that recent is- sues of this publication had gone far toward dispelling the fears of the craft anent the "overnight development" of television. Not so, it appears. Our mail continues to harp on this question, and a recently concluded extensive road trip proved this to be the first question asked in any gathering of projectionists. Our good friend and renowned tech- nician, Dr. A. N. Goldsmith, who knows all the answers, states concisely herein just what are the problems confronting television now and for some time in the future. Read it.
ONE of the most pressing projection problems is the tendency to run everything — carbon trims, generators, lamps — right up to the danger line or even beyond its particular rated capacity. Ratings of any projection adjunct are the result of careful testing and experiment- ation by the manufacturers thereof, and their recommendations should be closely adhered to. Maximum amperages are no guarantee of best results, as has often been proven in this field — apart from the fact that maximum amperages in- variably mean minimum equipment life and loads of headaches.
PROJECTIONIST servicing of visual and sound projection equipment is catching on nicely, thank you. A bit of work, a bit of expenditure and the will to be something more than merely a switch-thrower will handsomely reward efforts in this direction.
PRODUCTION schedules for the bal- ance of this year fail to bear out the oft-repeated promise of a vast increase in the number of colored motion pictures. Picture costs are already running away with themselves in straight black-and- white, and the addition of color vastly increases costs, including labor. Such color as is on view these days merely strengthens the impression of this depart- ment that there is nothing more satisfy- ing at this date than a well-lighted, ex- pertly turned out black-and-white job.
THE public press is now utilizing its news columns to announce that the NRA is dead. Their current rather timid approach to this topic merely mouths that which any enterprising trade journal with sufficient courage has said repeat- edly throughout the past year or more. Extension of the NRA for another two years, as requested of Congress, means only perpetuating the lush-handed con- trol of all industry by the big-business code authorities. Enough is enough.
NOTHING as yet from the U. S. Su- preme Court by way of a decision on the Tri-Ergon patent tangle. Projection rooms won't be mauled about for another month or so.
INTERNATIONAL PROJECTIONIST
February 1935
The Standard of
Comparison:
f
MAGNARC
34 to 65 Ampere High Intensity Arc Lamp
Individual carbon feed adjustment. Floating carbon holders with carbon ends guided to main- tain perfect crater formation. Magnetic arc stabilizer. Accommodates full carbon trim without resetting. Uses largest reflector ever employed in a projection arc lamp. Unique dowser com- pletely protects reflector when lighting arc. Ventilated reflector compartment. Unit design. Massive and rugged construction.
Into this lamp has been built the principles required to most efficiently utilize the advan- tages of the new low-voltage high-intensity arc.
Made By The World's Largest Manufacturer of Projection Arc Lamps
Write for Literature
J. E. McAuley Mfg. Co.
552-54 W. Adams St.
Chicago, 111., U. S. A.
INTERNATIONAL PROJECTIONIST
VOLUME VIII
NUMBER 2
FEBRUARY 1935
EFFICIENT OPERATION OF THE SUPREX CARBON ARC
W. C. Kalb
NATIONAL CARBON COMPANY
THE advent of the powerful D.C. high-intensity condenser lamp in the larger theatres and, later, of the reflecting type Hi-Low lamp in theatres of intermediate size, set a new standard of motion picture projection. Theatre- goers, by their increased patronage, have shown their appreciation of the brilliant screen illumination which the high-in- tensity arc provides and also of the higher level of general illumination which it permits.
The need for a more powerful source of screen illumination in the smaller theatres has long been evident. This need is more pronounced today than ever be- fore because of the growing popularity of color pictures. Color pictures require a higher level of light at the aperture plate than do black-and-white pictures, and their full color value is best realized with the snow-white projection light char- acteristics of the high-intensity arc.
To bridge the wide gap between the quality and intensity of light supplied by the high-intensity arcs in the large theatres and that available from the low-
intensity D. C. lamps used in the smaller theatres, the Research Laboratories of National Carbon Company, Inc., devel- oped new carbons which extend the field of the high-intensity arc into a lower current range than had previously been practicable.
These new high-intensity carbons an much smaller in diameter than have heretofore been used for projection. An- other point of difference is that they are copper-coated, whereas the positive car- bons of larger diameter are uncoated. This metallic coating improves the elec- trical conductivity, permitting operation at high current density without the use of a cooling head, and also allowing the carbon to be gripped at any desired dis- tance from the arc.
The new projection lamps developed especially for the use of these carbons are of the reflecting type but differ in several respects from the Hi-Low lamp and from the condenser type high-intensity lamp. These older types hold the negative car- bon at an angle to the positive which is gripped at a short distance from the arc
and rotated during operation. The new lamps are designed to hold both carbons in a horizontal position gripped at or near the end away from the arc, and neither carbon is rotated when the lamp is operating.
In the Suprex Type D. C. Lamp dis- cussed in this article, the axis of the neg- ative carbon, while parallel to that of the positive, is slightly lower. Compared with the low-intensity, D. C. mirror arc, these new high-intensity arcs provide a greatly increased volume of useful light. Improvements in the optical system are a further aid to their efficiency.
The crater of this small-diameter, non- rotating positive carbon assumes a cup- like form, the same as in the higher amperage lamps in which the positive carbon is rotated. The brilliancy of this crater is more than twice that available from the crater of the D. C. low-intensity arc. The light has the pure, snow-white quality which, in pleasant contrast to the yellowish tinge of the light from the low- intensity D. C. arc, has done so much to popularize high-intensity projection. The
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INTERNATIONAL PROJECTIONIST
February 1935
small diameter of the carbons, however, calls for accurate control of arc current and crater position in order to obtain full efficiency of light output and uniform distribution of light on the screen. For- tunately, this detail has been taken care of in a highly satisfactory manner by the lamp designers.
With a view to giving the projectionist data which will enable him to obtain the best possible results from this new pro- jection unit, there are here summarized the conclusions drawn from a study of this arc in relation to the light on the pro- jection screen. In actual practice there are several variables which simultan- eously affect the light on the screen, but in this investigation the effect of each variable has been studied independently. By combining the data obtained on these several variables, however, the resultant effect can be predicted.
Carbon Trims
Three trims are now available for these Suprex type D. C. lamps. These are shown in Table A.
The rate of carbon consumption is the same for all of these trims at correspond- ing limits of their current range. To illustrate, with the 6mm/5mm trim at 32 amperes, the 7mm/6mm trim at 42 amperes, or the 8mm/6.5mm trim at 56 amperes, positive carbons are consumed at an average rate of 6.5 inches per hour and negative at an average rate of 3.0 inches per hour. At the respective upper limits of current range — 40, 50 and 65 amperes — average carbon consumption per hour is 13.5 inches for positive and 4.5 inches for negative.
Since, at the present time, most of the lamps and auxiliary equipment in use have been designed to use the 7mm positive/6mm negative trim, the discus- sion of the effect of the several variables is based on studies of this trim in a typical lamp. The specific values men- tioned are applicable only to this trim, but the conclusions reached may be ap- plied, in a general sense, to the smaller and larger trims.
Proper Arc Length
If the arc current is held constant and the positive carbon maintained at a con- stant distance from the reflector, the arc length may be varied substantially with- out appreciably affecting the total light on the screen or its distribution. An arc length of 9/32" to 5/16" is usually main- tained with the 7mm/6mm trim. With a very short arc length, such as 3/16",
there is built up on the negative carbon a reddish deposit which, unless removed, may cause difficulty in restriking the arc. On the other hand, an arc length of %" or more introduces perceptible wavering of the arc which tends to cause a fluctu- ation in the screen light.
If the arc current be increased, while the arc length and the distance of the positive crater from the reflector be held constant, there is a very definite increase in the screen light but very little change in light distribution. An increase in arc current from 40 to 50 amperes, amount- ing to 25%, results in a 47% increase in the light on the screen. The ratio of brilliancy from center to sides of screen is slightly increased by this increase in arc current, but not enough to present an objectionable contrast. There is also an increase in crater depth and in rate of carbon consumption.
The rate of increase in carbon con- sumption, with increased arc current, is greater for the positive carbon than for the negative. If the arc is burned at too low a current, the crater is very shallow and the light is not uniform in color. On the other hand, at too high an arc cur- rent carbon consumption is excessive and the light is not steady.
If the distance of the positive crater from the reflector is varied, while arc length and current are maintained con- stant, marked variation in screen light and distribution result. Observations were made with a 7mm/6mm trim oper- ated with 5/16 inch arc length and 45 amperes arc current. Moving the posi- tive crater from a point 3.70 inches from the reflector to a point farther away causes a sharp increase in light. This reaches a maximum, representing 77% increase in total screen light, at a point 3.82 inches from the reflector. Further movement away from the reflector re- duces the total light, but at a slightly less rapid rate. At 3.90 inches from the reflector the total light is 49% above that at 3.70 inches, or 16% less than at the peak.
With the positive crater 3.70 inches from the reflector, the distribution "of light on the screen is uniform, the sides being as bright as the center. If the arc is moved closer to the reflector, the light at the sides of the screen becomes brighter than that in the center. This condition is very undesirable. Moving the arc away from the reflector causes a more rapid increase in brightness at the center of the screen than at the edges. After a point 3.84 inches from the re-
TABLE A
Positive Carbon
Negative Carbon
Recommended Arc Currents
Voltage Range
6mm Suprex Positive 7mm " 8mm "
5mm Suprex Negative 32-40
6mm " " 42-50
7mm or 6.5mm " 56-65
31-40 31-40 31-40
Figure 1
flector is reached, the contrast in bright- ness between center and sides of the screen becomes very noticeable.
The distance between the positions 3.70 and 3.84 inches from the reflector may be taken as an arbitrary range of satisfactory projection. This allows a range of only 0.14 inch for the arc posi- tion. With the 8mm/6.5mm trim this range is slightly greater.
Arc Control
This narrow range of arc position re- sults from a combination of four factors: the curve of light distribution emitted from the positive crater, the magnifica- tion of the optical system, the diameter of the crater opening, and the dimen- sions of the film aperture. None of these factors is under the control of the projec- tionist, so it is obviously desirable that the control mechanism of the lamp be adapted to maintaining the position of the arc within these limits. This is very effectively accomplished by a number of the lamps which are now on the market.
The ratio of the feed of the positive and negative carbons can also be regu- lated, either by provision for adjustment in the lamp itself or by a comparatively simple change in the lamp parts. From the figures on carbon consumption pre- viously given, it will be noted that the ratio of positive to negative carbon con- sumption is 2.17:1 at the lower limit of current range and 3:1 at the upper limit. Increase of arc current, without change of feed ratio in the control mechanism, will therefore tend to increase the arc length as the carbons are consumed; and reduction of arc current will tend to re- duce the arc length.
It is known that the voltage drop across the arc stream of the high-intens- ity D. C. arc from the positive to the negative carbon is comparatively low and does not increase materially as the cur- rent is increased. On the other hand, the voltage drop within the positive crater is comparatively high and does increase substantially as the current and crater depth increase.
As shown in an earlier paragraph, the
February 1935
INTERNATIONAL PROJECTIONIST
increase in voltage and crater depth which accompanies increase in arc cur- rent causes a very material gain in the useful light of the arc. If there is a dis- turbance in the high-intensity effect — for example, a decrease in the voltage drop in the crater caused by a crooked crater due to poor alignment of the carbons — ■ the resultant effect on the arc will de- pend upon the characteristics of the power source.
If the power source is 115-volt line or an 80-volt motor-generator set, a com- paratively large amount of ballast re- sistance is required to reduce this volt- age to the value of 31 to 40 volts re- quired at the arc. Consequently, a de- crease in arc voltage would cause only a small increase in arc current and ap- preciable time would be required to re- store the normal crater depth. Such a source is, therefore, undesirable from the standpoint of arc stability as well as that of economy.
However, if a power source with a no- load voltage near that of the arc and a falling volt-ampere characteristic curve is used, or a constant voltage source only slightly higher than the arc voltage and requiring a comparatively small amount of ballast resistance, then a disturbance resulting in lowered arc voltage would produce a decided increase in current which would immediately tend to restore the proper crater depth and cause a re- turn of arc voltage and current to normal conditions. A power source from which the current decreases with decrease of arc voltage is entirely unsuited, since the re- duced current would further decrease the crater depth and arc voltage and an unstable condition would result.
Several different types of units are now on the market which have characteristics suitable for these non-rotating, high- in- tensity, D. C. arcs. Each has its own peculiar advantages but all are character- ized by a comparatively large increase of current with a decrease in arc voltage. These units fall into three classes:
1. Low voltage motor generator sets with constant voltage characteristic. These are suitable for use with two lamps and their individual ballast re-
sistances, connected to the generator in parallel.
2. Motor generator sets with falling volt-ampere characteristic and a no-load voltage near that of the arc. These re- quire no ballast resistance but do re- quire a separate generator for each lamp.
3. Rectifiers with falling volt-am- pere characteristic which, likewise, re- quire no ballast resistance but require a separate unit for each lamp.
If a single-phase rectifier is used, the fluctuation in voltage and current may cause a noticeable beat in the screen light unless a sufficiently large choke coil is used on the output side of the rectifier. With two-phase and three-phase rectifiers the variation in instantaneous values of current and voltage is small and is not noticeable in the light on the screen.
Stabilizing Magnetic Flux
In the high-intensity lamps with rotat- ing positive carbon the negative carbon has always been placed at an angle to the positive. The lines of magnetic flux surrounding the carbons, generated by the current passing through them, are thus crowded together below the arc and spread out above it. This produces a magnetic force on the arc stream which, in conjunction with its natural flow, pro- jects the tail flame of the arc upward and forward from the positive crater, as shown in Figure 1.
The carbons in these new Suprex type lamps, however, are both held in a hori- zontal position and the magnetic field is uniform on all sides. The tail flame of the arc therefore surrounds the posi- tive crater in an almost uniform layer, as shown in Figure 2. This condition lacks stability, and slight disturbances, such as a slight change in the alignment of the carbons, may cause the crater to burn off on one side and produce a noticeable change in the light on the screen.
In some of these lamps an auxiliary magnetic field has been introduced which augments the magnetic flux below the arc and opposes that above it. This gives the tail flame a definite upward trend, as shown in Figure 3, and assures greater stability to the position of the arc stream and the form of the crater.
The axis of the negative carbon is placed slightly below that of the positive to compensate for the angular direction of the arc stream. The improvement in the steadiness of screen illumination re- sulting from the use of this auxiliary magnetic flux is very noticeable, especi- ally when the lamp is operated from a 115-volt line through a large ballast re- sistance. It is, of course, essential that this field be of the right direction, and care must be taken, when making any repairs to the lamp, to see that the direc- tion of this auxiliary flux is not reversed. Distance from positive crater to re- flector is the most important item in
Figure 3
the control of this arc. Variation in this distance causes decided variation in both the total screen light and the contrast in brightness between center and edges of the screen.
Ratio of positive-to-negative carbon feed should be adjusted so that uni- form arc length and position can easily be maintained at the desired operating current.
Increasing arc current increases pos- itive-to-negative ratio of carbon con- sumption.
Increasing arc current increases total screen light but does not greatly affect the light distribution, mat is, does not greatly modify the relative intensity of illumination at center and edges of the screen. Arc current should be held within the recom- mended limits for the trim in use.
Variation of arc length does not appreciably affect the total light on the screen nor its distribution, pro- vided the arc current and position of positive crater remain unchanged. Ex- treme variation of arc length, how- ever, introduces operating difficulties.
The most satisfactory source of power is a constant voltage source near enough to the arc voltage to per- mit the use of a small ballast resist- ance or a source with a falling volt- ampere characteristic and a no-load voltage not greatly in excess of the arc voltage.
With a suitable source of power and proper adjustment of the control mech- anism for the conditions under which the arc is operated, these new Suprex type, D. C, high-intensity arcs supply the long-felt need of the smaller thea- tres. They provide all the advantages of light quality and intensity which the higher amperage high-intensity lamps have given the larger theatres. They produce 100 to 200% higher levels of screen illumination than is available from the low-intensity D. C. mirror arc and at a lower operating cost per unit of light volume. They constitute one of the most striking of recent ad- vances in the art of motion picture pro- jection.
STEP-BY-STEP ANALYSIS OF SOUND REPRODUCING EQUIPMENT
Aaron Nadell
VII. W. E. Motor Control Cabinet
FIGURE 1 is a schematic diagram of an A. C. motor speed control cir- cuit using four vacuum tubes. The motor is shown at the extreme left. The motor proper consists of two parts, the stator and the rotor. The stator is sup- plied with alternating current through terminals 1 and 2 of the control cabinet. The 110-volt A. C. supply is wired to the two bottom terminals of the cabinet.
From these terminals the circuit can be traced right through the two 10-amp. fuses, F-l, thence through the safety switches D-3 and D-4, thence through switch D-l, by means of which this motor is started or stopped, and thence upward and leftward to the stator winding. (A branch circuit supplies the primary of the power transformer, T-l from the same power source.)
The A. C. flowing in the stator wind- ings generates an alternating voltage in the rotor. In other words, the stator windings may be regarded as the prim- ary, and the rotor windings as the sec- ondary, of a transformer. The rotor is equipped with brushes which are wired, through terminals 3 and 4 of the control cabinet, to a reactance coil, L-2. (That coil is readily found in the drawing by following the wire that runs right from terminal 3.)
Therefore, A. C. flows in the rotor windings, completing its circuit through the brushes and the reactance L-2. The alternating magnetic field created by this current reacts with the alternating mag- netic field that surrounds the stator, caus- ing the rotor to revolve.
The speed with which the rotor re- volves depends upon the strength of its field; the strength of its field depends upon the strength of its current, and the strength of its current depends upon the impedance of the coil L-2. Any influ- ence that can change the impedance of that coil will control the speed of the motor.
The Inductor Generator
An iron wheel of irregular outline is shown in the drawing just above the rotor. This is mounted on the rotor shaft and revolves with it. It constitutes one part of the inductor-type generator that is built into the same casing with this
motor. The other two parts of that gen- erator are the field (shown just above the rotating element) and the stationary armature, shown to the right of the field.
The field is supplied with D. C. through a rectifier tube (V-3) inside the control cabinet. Both the field and the armature are wound on an iron core. This core is equipped with a gap through which the projections of the rotating ele- ment pass as the motor revolves. Every time one of those projections enters or leaves the gap the strength of the D. C. magnetic field that surrounds the induc- tor field winding is altered, and a pulse of A. C. is generated in the armature winding.
When this motor is revolving at the correct speed of 1200 r.p.m. the current generated in the inductor armature is 720 cycles. When the motor revolves more slowly the projections of the rotating ele- ment enter the gap of the core less often per second, and the frequency generated in the armature winding is less than 720. When the motor speed exceeds 1200 r.p.m., the frequency generated in the armature is more than 720.
The A. C. generated in this armature enters the control cabinet through term- inals 4 and 6. It acts through the in- ternal circuits of the cabinet to vary the impedance of coil L-2, and therefore to control the speed of the motor.
The Bridge Circuit
Although this cabinet is designed to operate automatically to keep the speed of the motor constant at 1200 r.p.m., it may also be used in another way. By throwing a switch the automatic control is open-circuited, and the speed of the motor is controlled by hand, through a potentiometer knob on top of the cabinet. The motor can then be operated at any speed between 1,000 and 1,4000 r.p.m. The switch that permits the projectionist to select either manual or automatic con- trol is D-2, located at the top center of the drawing. Thrown to the right it provides manual control; thrown to the left, it switches in the automatic regula- tion.
Assuming that this switch is thrown to the left, the A. C. from the inductor armature is provided with two parallel
paths inside this cabinet. The circuit may be traced right from terminal 6 to the lower blade of switch D-2. At this point two paths divide. One runs right, down through the primary windings of T-3, and thence left to terminal 4. The other runs left through the lower blade of D-2, down through the retard coil L-l (and through the condenser built into that coil), thence down through R-13, R-14 and R-ll, and left to terminal 4.
One vital fact about this divided cir- cuit is that when the A. C. input is pre- cisely 720 cycles the impedance of the two paths is precisely equal, and the cur- rent divides 50-50 between them.
But when the frequency is either more or less than 720 cycles the impedance of the two arms is not balanced. At fre- quencies below 720, the retard coil L-l acts like a resistance in series with a con- denser. At frequencies higher than 720 it acts like a resistance in series with a choke coil. The reason for this is that the coil-and-condenser combination which constitutes L-l is tuned at the factory to offer minimum impedance at precisely 720 cycles. When any other frequency is applied, L-l no longer balances the up- per half of the primary winding of T-3.
When the current is 720 and the two parallel paths offer the same impedance, the voltage drop across L-l is precisely the same as the voltage drop across the upper half of T-3. Therefore, the poten- tial difference between the mid-point of T-3 primary and the lower end of L-l is zero, and no current flows across the "bridge" (the double primary of T-2). But when the current is other than 720 cycles, the voltage drop across L-l is not the same as the drop across the upper half of T-3 primary. Under such cir- cumstances a potential difference exists between the lower end of L-l and mid- point of T-3 primary, and current does flow across the "bridge."
This "bridge" consists of the two para- lleled coils constituting the primary winding of transformer T-2, and of the condenser C-6, which is in series with that primary.
At frequencies below 720 cycles the effect of L-l and C-6 is to place the cur- rent through T-2 primary 180 degrees out of phase with the current through T-3 primary. Conversely, at frequencies above 720 the currents through the two
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February 1935
INTERNATIONAL PROJECTIONIST
11
primaries are in phase. At exactly 720 cycles there is, as just said, no current at all through the primary of T-2. This phase-change of 180 degrees, when the frequency of the inductor current passes through 720 cycles, controls the speed of the motor by acting through the vacuum tubes to increase or decrease the imped- ance of coil L-2.
The filament of tube V-4 is heated with A. C. derived from the third second- ary of the power transformer T-l. The plate of this tube is supplied with 720- cycle A. C. through transformer T-3. V-4 is called the "detector" tube of this cab- inet. Its operation may be made clear by describing it as a grid-controlled recti- fier, which in fact it is.
V-4 is given three sources of grid bias. The first is a voltage drop existing across R-8, the resistor just under V-3. We may trace the bias circuit from the left-hand side of V-4 filament right to the upper or positive end of R-8, down through R-8 and left through the bias-adjusting ar- rowhead ; thence down, left and up to the right-hand, or positive, side of R-2, the voltage drop across which is the second source of grid bias for V-4; thence up through R-3, R-4 and R-5, to the right- hand side of T-2 secondary.
The 720-cycle A. C. generated in this secondary constitutes the third source of grid voltage for V-4, serving to in-
crease and decrease the fixed bias 720 times a second. From the left-hand side of this secondary upward and right through the upper blade of switch D-2 to the grid of V-4. Condensers C-2 and C-3 filter the current flowing through R-2, and thus steady the bias of V-4.
Now, remembering what has just been said of the phase relations between the transformers T-2 and T-3, it is plain that when the inductor current is less than 720 cycles, the grid of V-4 will swing negative while the plate of V-4 is posi- tive. Since space current can flow through any vacuum tube only when its plate is positive, the grid of V-4 will be more negative during the only part of the A. C. cycle that matters to the tube, and the space current through the tube will be lowered.
On the other hand, when the inductor output is more than 720 cycles, the grid of V-4 will swing positive (less negative bias) while the plate is positive (which is the only time that matters), and the space current through V-4 will be larger.
Therefore, at motor speeds above 1200 the space current through V-4 is relative- ly large. At motor speeds below 1200 the space current through V-4 is relative- ly small. The space current through V-4 is used to control the bias of the grid- controlled rectifiers V-l and V-2.
V-l and V-2 operate in a full-wave rec-
tifier circuit. Their filaments are sup- plied by the second secondary of the power transformer, T-l. Their plates are powered by the topmost secondary of that transformer. The grids are main- tained at a positive bias by means of the voltage drop through resistor R-8, which is seen just under tube V-3; but the volt- age drop through resistors R-6 and R-7, under V-4, tends to counteract this bias.
Tracing from the grids of V-l and V-2 upward, this circuit runs to the lower, or negative, end of R-7, through the re- sistors and up to the left-hand leg of V-4, thence right to the upper, or positive, end of R-8, down through R-8 and left at the arrowhead grid bias contact, down, left, down through the milliameter and right to the filaments of V-l and V-2.
Condenser C-7, which is shunted around resistors R-6 and R-7, serves to filter the half-wave voltage drop through those resistors and to steady its effect upon the grids of V-l and V-2.
At motor speeds above 1200 r.p.m. the space current through V-4 is, as just ex- plained, relatively large, consequently the voltage drop across R-6 and R-7 is rel- atively large, and the grids of V-l and V-2 swing toward negative. Under those conditions the space current across these tubes is reduced. At motor speeds below 1200 r.p.m., the space current through V-4 is relatively small, the grids of V-l
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INTERNATIONAL PROJECTIONIST
February 1935
and V-2 become more positive in bias, and the space current across these tubes is comparatively large.
The space current of V-l and V-2 may be traced through its circuit as follows: from whichever end of the top secondary of T-l may be positive at the moment to the plate of the corresponding tube, through the vacuum to the filament, left from filament and up through the millia- meter.
Here the current divides: one branch flows through resistors R-2 and R-l to provide grid bias for V-4; while the other branch flows through the coil shown just below these resistors. At the left-hand end of that coil the two branch- es reunite and the circuit continues down and left to the center-tap or negative terminal of the secondary of T-l. The condenser C-l serves as a filter to steady the rectified current through the coil, and prevent "hunting" in the motor.
Saturated-Core Reactance
The coil through which the rectified current flows is wound on the same iron core with L-2, and constitutes part of the 144-A retard coil assembly. At low cur- rent values through V-l and V-2 (corre- sponding to motor speeds above 1200 r.p.m.) the impedance of coil L-2 is com- paratively large, thus reducing the rotor current and, consequently, the speed of the motor. At high current values through this rectifier (motor speed low) the core of the 144-A retard assembly is saturated by the rectified current — that is, magnetized as completely as it ever can be. This fact operates to decrease the impedance of the winding L-2, there- by permitting the rotor current to in- crease, and