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250 PROJECTION SCREENS COMMITTEE [j. s. M. p. E.
Light Transmission. — The light transmission may be varied to meet different requirements. We have already seen that transmission may be made to favor any particular color. It also may be made to give several different types of distribution. By proper processing, the distribution is made more uniform, and hence satisfactory for viewing at wider angles. It must be expected that there will be an additional loss of contrast as compared with front projection because of the introduction of another translucent surface, which adds to the flare effect.
Illumination.— Since the screen is light transmitting, the light intensity in the auditorium can be considerably higher than in the ordinary theater during a performance. It has been stated that the auditorium is illuminated to about 30 per cent of average theater full lighting. Nevertheless, it is necessary to take precaution to keep light from falling on the screen, in as much as there is some slight reflection from the surfaces. High auditorium illumination means that confusion in seating is practically eliminated. For types of theaters where patrons are continually passing in and out, it is very desirable to have considerable light. However, it must be remembered that a partially lighted auditorium tends to prevent patrons from "living" through a feature presentation, since it makes one too conscious of his immediate surroundings. In a theater showing newsreels and short subjects, this is not objectionable.
For much of the above information on rear projection we are indebted to Mr. W. Mayer and the Trans-Lux Movies Corporation.
•S. K. WOLF, Chairman D. S. DE'AMICIS W. F. LITTLE
F. M. FALGE A. L. RAVEN
H. GRIFFIN C. TUTTLE
DISCUSSION
PRESIDENT CRABTREE : The work of this Committee points the way in which a committee can do real research work. They did not have to have a research laboratory in which to make these tests. They used the available research laboratory, which was the membership of the Society. I congratulate the Committee on this pioneering effort in cooperative research.
It is very interesting to find that it seems to be necessary to have a greater screen brightness for the outdoor shots than the indoor ones. On second thought, it is reasonable. Probably the matter could be taken care of by giving a uniform flash exposure to the interior scenes, or they could be printed a little heavy.
With reference to the brightness test I should like to point out that the figures show approximately ten foot candles as the minimum desirable brightness of a picture. In previous years we have made numerous tests of screens, and find that