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1945 Theatre Catalog, 4th Edition, Page 334 (310)

1945 Theatre Catalog, 4th Edition
1945 Theatre Catalog
1945 Theatre Catalog, 4th Edition, Page 334
Page 334

1945 Theatre Catalog, 4th Edition, Page 334

the entire pressure plate, greatly prolonging life. Ball thrust bearings insure smooth operation, an essential to perfect sound and projection.


Good picture projection can be obtained only with high-quality equipment, properly installed and adequately main' tained. Generally speaking, the theatrical industry has long recognized this fact. In addition, however, it is now realizing the desirability of coordinating units to obtain the highest possible performance.

Research by the Academy of Motion Picture Arts and Sciences, by the Society of Motion Picture Engineers, and by various equipment manufacturers, has established the fact that accurate coordination of the various pieces of equipment is a prerequisite of optimum performance.

For instance, the size of the arc lamp and its operating current, the shutter cut-off time, the effective aperture of the projection lens, and the screen size and surface, all control the apparent screen brightness level, as visible to the audience. If this brightness level is too

low, the picture is dim; if it is too great, any defects in projection are emphasized and shutter flicker may become objectionable.

This latter condition is usually immediately apparent if the projector is operated without film, throwing brilliant white light on the screen. If the screen illumination level is adequate for good presentation of Technicolor pictures, and a light black-and-white film is shown, any defects in projection caused by unsteady machine operation, or improper design, may be painfully apparent.


The type of screen surface will be governed somewhat by the length-towidth ratio of the seating area. A silver screen may be used in a long, narrow house, whereas in a wider house a uniformly diffusing screen, such as the RCA Showhite, is required to insure good visibility at the side seats. The wider house will therefore require more light on the screen to provide suitable screen brilliance for side seats; this necessitates a larger and more powerful lamp, with its increased current drain. Naturally, a larger arc-lamp supply will then be required.


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It would be desirable also for the operator or theatre owner to consider using a projector which, like the Brenkert type BX-SO, has both shutter blades between the lamp and the projector aperture, where both blades are edective in keeping heat from the film, as well as in producing the quickest possible cutod of the light beam. Quick, complete cutoff gives maximum screen illumination with minimum travel ghost, thus saving light and aiding in obtaining a sharp, brilliant picture.

If a large screen picture is required, any jump or weave of the film as it passes through the projector aperture will be magnified to a greater degree on the screen. Thus, a projector which reduces film unsteadiness to an absolute minimum will be required. The Brenkert projector meets this requirement, and will continue to do so for a long time, because of its balanced design, oversize parts, and positive-feed continuous oiling system. This oiling system utilizes a circulating pump and an oil splash system, just as an automobile engine does. It will be remembered that automobile engines were never satisfactory prior to the development of this type of lubrication system; now, they operate satisfactorily and develop little wear or noise even after years of operation, with no attention to lubrication other than occasional oil changes. The same thing is true of Brenkert projectors.

Lamp and Light

The projection arc lamp also must be coordinated with the rest of the equipment. Numerous types of lamps are now available in various powers and designs; but quite often prospective purchasers are puzzled as to which type to buy. The most efiicient lamp is the one which puts the largest amount of light into the projection lens and on the screen in proportion to the power consumed. This naturally results in the lowest possible electric bills. Because the arc lamp is the largest consumer of power in the projection room, any saving in electric current it uses amounts to a considerable sum of money in a years time.

Part of the light given off by the positive carbon crater and the arc gas is collected by a reflector, and concentrated on the film at the aperture. If all the light given 06 by the arc could be collected and passed to the screen, the lightutilization of the lamp would be perfect. Unfortunately, this is impossible. In order to collect all the light produced, the arc would have to be completely enclosed by a perfect mirror. Naturally, no light could then escape or be reflected to the projection lens. In practice, therefore, the arc is only partially enclosed by a mirror. This mirror is large enough, and so placed, as to collect as much light as is practicable. Light reflected from any point on this mirror will travel in a straight line from that point: the light from the arc will be reflected to the film aperture. To insure even illumination over the entire aperture, and therefore over the film picture, the spot of light is made slightly larger than the aperture.

The light which passes through the film will be somewhat scattered, or dif CATAlOG-l945
1945 Theatre Catalog, 4th Edition, Page 334