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August, 1953
HOULT, HARPER AND STAFFELL [ PROCESS PROJECTION IN COLOUR
41
Fig. 3. The J.A.R.O.
Still Plate Projector.
Multiple Projector Set-ups
The triple-head projector was made to provide three times the screen brightness possible from a single-head projector. This is achieved by superimposing three separate images on the one screen, by the use of crossfronts on the lenses.
There are also occasions when it is required to superimpose the images from two or more of our single-head projectors, either for the same purpose or to give added flexibility to the set-up ; or it might be required to superimpose the projected image from a moving and a still projector, such as when a cloudscape from a still plate has to be used with a seascape from a moving plate.
Having described the available equipment 1 should now like to describe my ideal 35mm. projector which, like all ideals, will probably never be realized. It would have the following features : —
(1) absolute steadiness of the projected image over an area of 24-ft. by 18-ft.,
(2) minimum buckle of film while exposed in the gate,
(3) light output not less than 50,000 lumens at 200 amps.,
(4) inaudible to sound recording when placed 20 feet from a 10-ft. by 8-ft. screen,
(5) maximum accessibility and speed of operation on the floor,
(6) minimum of maintenance,
(7) a range of objectives of focal lengths 4-ins., 5-ins., 6-ins., 7-ins. and 8-ins.,and
(8) an optical system with an aperture of f/1.4.
Some of the lenses might prove a nightmare to the optical manufacturer, but we are now using a 4-inch f/1.4 lens, which might well prove to be the shape of things to come.
Modern Projection Screens
-front
Process screens are of two typesprojection and back projection.
The requirements of front projection screens are relatively simple. A diffusing