International projectionist (Jan-Dec 1954)

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Vol. 29, No. TO ^ summary of opinion which, while relating to a specific situation, applies with equal force to the fundamental requisites of the art of «/isual and sound projection. The appended expressions of various viewpoints reflect IP's policy of providing a forum for anybody who has anything interesting to say anent the projection process. A Case In Point: Top-Notch Projection Demands Top-Notch Equipment To the Editor of IP: Our efforts to increase our screen light embraced, among other things, the idea of using water-cooling for our lamphouse. Is is a fact that through the use of water-cooling jackets we will actually lose light? This seems to be a very controversial subject in projection circles, thus our appeal to IP for factual information. The basic problem is simple: how can we increase the light on our screen? Our equipment set-up is as follows: a pair of Gardner heads with barrel-type shutters, with the shutters trimmed down to the point where we get a slight travel-ghost; Kollmorgen 4-inch, //2 coated lenses; Strong Mogul lamps; metal reflectors; carbon trim of 8 x 9 Orotip Suprex, pulling 75-80 amps; RCA tube recti fiers for 40-volt, 80 amp, 3-phase; projection throw 250 feet. Formerly our screen was 35 x 48 feet, surfaced with white asbestos siding (Johns-Manville) . Now that we are converting for CinemaScope, we plan upon a screen 35 x 78 feet, with the same J-M siding. Light is our chief concern, as you will understand. Any assistance you axe able to render will be greatly appreciated. I think that you have a wonderful magazine. Other publications give me this "canned" information, but I have learned through the years to rely upon the integrity of IP. John "Pat" Elzey Pat Drive-In Theatre, Vidalia, Louisiana. IP's Viewpoint: IT IS our impression that the light on your present screen is somewhat less than you would like it to be. And, as you are aware, the light will drop to about half its present level when you change to CinemaScope — unless something is done to increase it. The obvious and most effective remedy is, of course, the purchase of more powerful lamps together with appropriate rectifiers. This, as you say, is out for the present, so we'll see what can be done for a smaller outlay of cash. First thing, we'll advise you not to spend money for something you don't need just now, and which will decrease, not increase, the brightness of your picture. We are talking about carbon-cooling water jackets. These devices improve the quality of the light, and they also make satisfactory operation of the lamps much easier; but they always decrease light-output by about 15% unless the carbons are already overloaded. Carbon coolers increase light with an overloaded trim by preventing spindling, thus enabling a larger, somewhat shallower crater to be formed in the end of the overloaded positive carbon. This holds the luminous ball of ionized gas at the tip of the carbon and prevents it from streaming out as an oversize tail-flame. The tail-flame adds little or nothing to screen illumination. Your 9-8 mm trim, however, seems to be a trifle underloaded; and the use of carbon coolers in your lamps with your present rectifiers will decrease your screen illumination by at least 15%, and possibly more. The water-cooled crater is slightly larger INTERNATIONAL PROJECTIONIST • OCTOBER 1954