Moving Picture World (Jan-Feb 1927)

January 1, 1927 MOVING PICTURE WORLD 79 Bluebook School Answer No • 544 Note : — This “School” is designed to arouse interest in the study of those many problems which constantly arise in motion picture projection, AND to cause men to really study the Bluebook and assimilate the vast amount of knowledge contained within its covers. Suppose you are employed as projectionist in a large theatre under construction. Your employer asks your advice concerning the type of light source it is advisable to use for projection. Just what various things would you give consideration, and what information would you desire before offering advice ? This question was asked by G. L. Doe, of Chicago, who challenged Broadway men to answer it : It is a rather astonishing fact that Chicago’s bluff was NOT called by New York City. Not a single “Broadway” man even tried to answer. I shall not comment on that fact further than to say that it is NOT to the credit of Broadway. The following gave the question a whirl, though several frankly stated that they felt incompetent to deal with it fully. John Griffith, Ansonia, Conn. ; W. C. Budge, Springfield Gardens, N. Y. ; G. L. Doe, Chicago, 111.; John, “Bill” and “Jack” Doe, Chicago, 111.; C. H. Hanover, Burlington, Iowa; Thomas H. Namard, Waltham Theatre, Waltham, Mass.; E. Fergodo, Livermore, Calif. ; Charles E. Curie, Chattanooga, Tenn. ; A1 Lichman, Glenside, Pa.; Allan Gengenback, New Orleans, La. ; Gilbert Atkindon, Cleveland, Ohio; F. D. Orenbacher, Truesdale, Mo.; T. R. Bankerton, Wentzville, Mo.; G. R. Hahn, Memphis, Tenn.; G. D. Thompson, San Diego, Calif.; Albert Joyce, Redwing, Minn., and D. G. Henderson, Quincy, 111. A good many of the answers did not get very far, but some of them did, and those who did not get very far at least had the energy to try. Griffith, Curie, Hanover, Namard, G. L. and “Bill” Doe, Budge and Livermore all did themselves credit, and most of the others made at least a fair stab at it. On the whole I believe G. L. Doe probably handles the matter best. He says : The first consideration would naturally be the severe brilliancy demanded by the conditions, and that would be directly affected by three major items, namely: the distance screen to rear rows of seats, the general illumination to be maintained in the auditorium, particularly in its forward part, while projection is in progress, and the color of the auditorium decorations, especially those close to the screen, which latter might perhaps interlock somewhat with the intensity of auditorium illumination. The necessary brilliancy of the screen surface to secure the desired effect involves the total amount of light incident upon its surface and the total area of the screen surface, which, in turn, interlocks with the reflective power of the screen and the direction of reflection necessary to best results in the ! individual auditorium. (About the most ' complete statement of such a problem I have ever seen. Ed.) Theoretically it is possible to calculate all this with a fair degree of accuracy, but I would personally consider the problem as j one in which experience would cover the I matter as well, or even better than it would i be possible to deal with it by calculation. , My reason for this letter is that not only must all the things I have, named be considered, but also the efficiency of the optical system of the projectors, the efficiency of the light source itself AND THE EF FICIENCY OF THE PROJECTIONIST have a very large bearing on t’he matter. Nor would I feel that I had me right to ignore the latter consideration entirely. I would personally feel that it was up to me to recommend a light source which I felt would supply plenty of light, even when not handled with high efficiency. Even though I felt that I could myself, by handling the light carefully and with high efficiency, get enough light with a Mazda, but that unless handled efficiently it would not supply enough light, then I would not recommend it. No man knows what tomorrow may hold, and in a week I might be gone and a man who would not Handle the light efficiently, through lack of knowledge or just plain lack of ambition and energy to do his work right, would be in charge. I would therefore recommend a source which would, to me, be over-efficient. Also it must be considered that the light source which would supply sufficient screen brilliancy when working at its maximum with a bran new screen surface, would not supply sufficient after the surface had become dulled by the inevitable deteroriation which starts the day the screen is put in place, and continues relentlessly as long as it remains — a slow but sure process. Another thing is that no authority has as yet even made a real attempt, so far as I know, to standardize the brightness of screen surfaces for various theatre conditions: also I understand our editor does not believe it possible to set up a standard of this sort. (Right, Brother Doe, because of the enormously varying conditions. Brother Griffith, in his answer, remarks that he believes it well to aim to secure at least 20 candle power for large theatres and 15 for small ones, but again this necessity involves the ENORMOUSLY important item of CONTRAST, hence I doubt the feasibility of the suggestion. Ed.) So much for the general discussion of the problem. Let us now look at the. various sources, which are the Mazda, the A. C. arc, the D. C. ordinary arc, the A. C. and D. C. reflector type lamp and the high intensity. We may promptly discard the A. C. arc as to all intents and purposes obsolete for projection purposes. If the exhibitor would not get a current rectifying device I would regard him as projectionally hopeless, and would leave him right then and there, and that, as our editor says, would be that. The straight (ordinary) arc is “out” these days also, because far better light sources SPECIAL ROLL and MACHINE TICKETS Your own special Ticket, any colors, accurately numbered; every roll guaranteed. Coupon Tickets for Prize Drawings 5,000 for $7.00. Prompt shipments. Cash with the order. Get the samples. Send diagram for Reserved Seat Coupon Tickets, serial or dated. 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It also is cheap in operation and not high in the item of malntainance. If it be a large, wide auditorium — one in which the distance rear rows of seats to screen is say 150 feet or more and a ‘screen of high diffusive power is necessary— it then follows that we shall need all the light it is possible to get, which means just one thing, viz.: high intensity. I know there may be those who will dispute on that last, but just the same I think the reflector type lamp cannot yet equal the high power high intensity in light production when working With a projector optical train. Between those two extremes it is my opinion that the reflector type lamp is the thing, the condenser and no-condenser types being a matter the individual must settle for himself. I don’t know enough to give an opinion on that point. To sum up: if the auditorium be a small one, narrow and not too deep (front to back) I would recommend Mazda. I would also recommend to the exhibitor the use of a not-too-light decorative scheme. If it be a small auditorium, but rather wide, requiringa highly diffusive screen, I would inform friend boss that while Mazda probably would serve fairly well, still reflector type lamps at low amperage would serve better, because it would give a reserve of light to use on dense film and we would be able to get almost any screen Williams desired. If the auditorium be both wide and deep, seating, say in excess of 3,000, I would recommend high intensity, with the notation that if the maximum viewing distance be not to exceed 125 feet, then a reflector type lamp will probably give satisfactory results, and at much less cost. If the auditorium be anything between the two extremes named, then I would certainly recommend a reflector type equipment, because of the fact that they have a wide range of light producing power and produce the light very efficiently, no matter what proportion of their possible range of light production be used. Gentlemen, that is, I hold a remarkable answer. It is an answer which does E-rother Doe distinct credit. I wish we might know the real name of the individual which produced it. Chicago certainly put one over on New York this time, because there were two other excellent answers from that city, whereas, though Brooklyn is represented, and a fairly good answer, too, not one man from New York City properly tackled it. It would not be fair to assume they were afraid to, but there certainly will be those, particularly in Chicago, who will hold that view. Brother Griffith’s answer contains a material which justifies me in giving it space in condensed form. He says : This question would run t’he whole gamut of projection knowledge if a complete answer be given. That is especially true if