Moving Picture Age (Jan-Dec 1922)

February, 1922 MOVING PICTURE AGE 29 MITROE SUN SCREEN "The Unequalled" Produces heretofore unattained Plastic — Definition — BrilliancyGives exceptional results in DAYLIGHT The proper screen for Churches, Schools, Colleges, Halls, etc. Produces soft, pleasing pictures which will not impair eyesight. Samples and further information on request Walker Motion Picture Service, Inc. 63 Fifth Ave., New York City Mechanics of Visualization (Continued from page 17) screens are well adapted to theatres in which the position of the seats with respect to the screen is such that the picture must be viewed at relatively large angles, for, no matter from what angle the screen is viewed, the brightness is the same because of the way in which the light is reflected. Aluminized screens and ground-mirror screens, on the other hand, are examples of the limited-spread or narrow-angle class. A clean aluminized screen can be designed to reflect about 60-65 per cent of the light striking it, and will confine the reflected light to within an angle of 30 degrees. Ground-mirror screens when clean can be made to reflect approximately 80-90 per cent of the light and confine the light to within about 30 degrees. Such screens are well adapted to theatres in which the seats are so arranged that the picture does not have to be viewed at large angles. It is well to emphasize the fact here that the foregoing reflection factors take for granted a clean screen surface. A very slight accumulation of dust can reduce the screen brightness very materially. There should be a regular schedule for cleaning the screen thoroughly, say so many times a week, or just before each show. Extraneous light has much to do with the screen brilliancy. Obviously a higher screen intensity is required in a theatre or hall into which daylight is allowed to enter or where lights are kept burning at all times, than in one where all the light comes from the projection equipment. The effect of extraneous light is to decrease the contrast between the high lights and the blacks and half-tones on the screen. If, for example, the intensity of the beam in a dark portion of the film is, say, 1/50 foot-candle at the screen, and in high light the intensity is, say, 2 foot-candles, the contrast is 1 to 100. If upon the screen image is now superimposed an intensity of 1/10 foot-candle, due to extraneous light, the contrast becomes approximately 1 to 17. From this it is apparent that even a very low intensity of extraneous light calls for considerable increase in screen intensity if good contrast is to be obtained. Hence at all times, especially where a projector of rather low power is being employed, there should, if possible, be no extraneous light of any kind while projecting. Motion Picture Projector Connects to any lighting socket without special wiring — simply screw the plug on the extension cord into any lighting socket and the universal motor and standard Mazda Lamp are ready or use. The Zenith is most moderately priced, and yet offers the dependable stability and the perfect projection of the strictly professional model, even at long distances. Very easily operated by even the inexperienced. Portable, safe, takes any standard film, fully guaranteed. Weight 50 lbs. Stereopticon attachment. Safety Projector Company f 310-312 West Second Street Duluth, Minn. Write for new catalog, just off press. Please mention this magazine. =zm-wrJ > ! ™mkl ft Visualize for the children Make education entertaining and lasting Please say, "As advertised in MOVING PICTURE AGE," when you write to advertisers.