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Polygonal Floodlight Mirror — Benford and Palmer 121
relativel}^ large area. These polygonal reflectors were constructed for use with 3000 watt tungsten lamps and we have been using 45 of them in a color motion picture studio in Rochester. They have proven very satisfactory for flood lighting and have a very high coefficient of utilization. In general a group of nine of these are assembled fairly close together, but even so the spatial distribution is relatively great so that the shadows formed are not very distinct. In case a sharply defined shadow is wanted we find it necessary to use a spot light such as a 10 KW lamp mounted in a parabolic search light reflector.
Mr. Mayer: I should like to gather more information with regard to concentrating a beam of light from such a mirror. Would it be possible to concentrate the light by mirrors, that is, the smaller the individual mirror and the more of them, the greater the concentration?
Mr. Benford: Yes.
Mr. Richardson: Is it not a fact that the shadow effect is one application of the umbra and penumbra?
Mr. Benford: Yes.
Drs. A. R. Irvine and M. F. Weyman report (J. Amer. Med. Assoc.) that more eye-fatigue was caused by 45 minutes reading than view^ing black and w^hite motion pictures for II/2 hours, one hundred and fifty persons being examined. No less than 68 per cent of the subjects showed a 43 per cent loss of acuity of vision after 45 minutes reading and only 21 per cent after seeing the pictures. ''An interesting side-light on this observation was that when a group had been reading for 45 minutes and w^as sent immediately into a projection room, and view^ed a picture for 11/2 hours, 83 per cent of those who had showed a fall showed an improvement after seeing the picture." This is explained by assuming that the subject was bodily tired or totally fatigued on entering the room, and the entertainment of the picture provided relaxation for them. In other words when your brain and eyes are tired 'go to the movies.' In another group of 60 persons it was found that 53 per cent showed loss of acuity after seeing black and w^hite pictures, while only 48 per cent showed loss of acuity after seeing colored pictures of the Technicolor type. In another group of 153 people there was no difference in black and white and colored pictures. (Sci. Amer. 1927, 83, 343.)