Exhibitors Herald and Moving Picture World (Apr-Jun 1930)

April 12, 1930 Exhibitors Herald-World 113 BETTER PROJECTION A Department Conducted for Both Projectionist and Exhibitor By F. H. RICHARDSON— — The Rear Shutter and Film Ignition RECENTLY I received a letter from the president of a company manu facturing one of the leading projectors, in which he called my attention to a mistatement by me concerning the reduction of heat effected at the aperture by the rear shutter. Although the error was made inadvertently, it nevertheless was an error and I am only too happy to correct it. In the February 22d issue of the Herald-World, I said, “By installing this attachment [the rear shutter] you cut down the heat on the film by at the very least calculation, 75 per cent . . .” Now, gentlemen, I had no earthly intention of saying anything like that. But I did — and I apologize, both to you and to the executive who made the inquiry. What I had intended to stay in that place was what I did say at the beginning of that article, that is, “this particular new addition to projection equipment [rear shutter] reduces the probability of the FIRING of film at the projector aperture by at least 75 per cent.” As to the heat itself on the film, I should have said, “By installing this attachment you cut down the heat on the film by about 50 per cent . . .” Unfortunately, to be human is to err, at least once in awhile, and in this business of beating out thousands of words on a typewriter, it should occasion no surprise that the wrong words sometimes do get into one’s statements. When they do, I am only too glad to have them pointed out to me so that I may correct them. Now, as to the reduction in the probability of firing the film effected by the rear shutter: I really believe that the reduction does amount to at least 75 per cent. Of course, it would be difficult to prove that such an amount is correct, but I think it is entirely possible, for the following reasons: T IRST, with the entire heat of a light beam such as is sent forward by modern high intensity arcs, by reflector type arcs, or even by high amperage ordinary arcs concentrated upon the aperture, the temperature is very high. It is sufficient even to warp the frame of projector mechanisms. It will fire film almost in SORRY • REGARDING the published statement that I had arranged to supply locals asking for samples of wide film, what I said was then entirely time, but it seems now the official who made the agreement later took it up with other officials, with the following result: “Dear Mr. Richardson: I am sorry to advise that it will be impossible to furnish the promised samples of Grandeur film at present. I have taken the matter up with the executives of the organization and they think it inadvisable to carry out the plan at the present time. However, as soon as the film has become standardized I will be very happy to let you have them.” Personally, I don’t think that such changes as may be made will be of importance in this particular thing. However, I can understand that the officials of the company would prefer not to let the film samples go out, except in its final form. The S M P E standards committee is working now trying to effect a final standard width for wide film and we may expect that the matter will not be very long delayed. Meanwhile, any local unions desiring a sample may advise me. I have 16 such requests on file from locals now. The samples will be sent as soon as they are available. stantly, the heat of adjacent metals helping to increase the speed of firing, at least to some extent. The rear shutter eliminates at least half of this heat. It reduces the heat of even the hottest light beam to such an extent that the hand may be placed and held on the projector mechanism parts quite close to the aperture without serious discomfort, and, except when the most powerful arcs are used, without any discomfort at all. The heat is in fact reduced to such an extent that I have myself held a finger in the light beam at the aperture (no film in), using a 180ampere high intensity lamp, for a period of (as I remember it) two or three seconds, before feeling discomfort. And as you very well know, such a light source certainly does make a spot rivaling His Satanic Majesty’s dominions in temperature when using the old style shutter. Now, gentlemen, I believe that after you have considered all this, you will agree that when I say the danger of firing the film at the aperture is reduced by 75 per cent by using a rear shutter, I am well within the probabilities. I WOULD like to hear from projectionists as to their opinion upon this point. I also cordially invite both the correspondent, other projector manufacturers and projectionists to make the following experiment: First, place all reels of film in the film tank. Second, remove all other film from the room. Third, make your experiment only when no audience is present. Fourth, cut several strips of ordinary inflamable film, say three inches long. Fifth, have a man there with a watch to do the timing. Sixth, place your film over the aperture just as the second hand of the watch reaches one of the main divisions of its dial. Seventh, open the mechanism casing door on the working side. Open the gate. Strike the arc and let it get burning normally with the dowser down. Eighth, set the projector rotating shutter (rear shutter) so the light beam will pass through to the aperture. Ninth, holding one of the three and a half-inch long strips of film with a plyer. When the second hand reaches any suitable point, quickly place the film as flatly as you may over the projector aperture until it fires — not merely curls up, but bursts into flame. Note as nearly as possible the precise time. Repeat the experiment several times and then average the time required to fire the film. Next, start the projector at regular normal projecting speed and repeat the experiment several times. Average the time of these experiments also. The two averages will provide us with exact figures from which the exact percentage of difference in time of firing, as between rear and front shutters, may be obtained. This is a matter of large importance. I shall hope to hear from at least a thousand of you. Double that number will be better. Get thee busily busy. Our correspondent is especially invited to submit results of such an experiment, because he and other projector manufacturers have facilities for doing very exact work.