Movie Makers (Jan-Dec 1949)

372 GUIDES FOR GOOD PROJECTION Need a beaded or matte screen? Large or small in size? Here are the facts to aid you in answering these and other screening problems JAMES M. WHITNEY, ACL LENGTH TIME IN FEET SILENT (16) SOUND (24) 8mm. 16mm. MIN. SEC. MIN. SEC. % 1 2.5 1.7 i 2 5 3.3 2 3 7.5 5 4 10 6.7 2% 3 5 12.5 8.3 6 15 10 3% 7 17.5 11.7 4 8 20 13.3 4V2 9 22.5 15 5 10 25 16.7 6 12 30 20 7 14 35 23 8 16 40 27 9 18 45 30 10 20 50 33 11 22 55 37 12 24 1 0 40 13 26 1 5 43 14 28 1 io 47 15 30 1 15 50 16 32 1 20 53 18 36 1 30 1 0 20 40 1 40 1 7 22 44 1 50 1 13 24 48 2 0 1 20 26 52 2 10 1 27 28 56 2 20 1 33 30 60 2 30 1 40 32 64 2 40 1 47 34 68 2 50 1 53 36 72 3 0 2 0 38 76 3 10 2 7 10 80 3 20 2 13 42 84 3 30 2 20 44 88 3 40 2 27 16 92 3 50 2 33 48 96 4 0 2 40 50 100 1 10 2 47 PROJECTION FOOTAGE and screen timetable above— for 8mm. and 16mm., silent and sound films— will guide projectionist in timing narrative and musical scores. GOING to have a few friends in soon to look at last summer's pictures? Going to show your travel films at the local movie club to a hundred or more people? Whether at home or in a hall, a good projection job is equally important to your picture's success as are its camera work, editing and titling. There are, in projection, certain facts and figures which will be helpful. Movie Makers presents them on these pages, as amateur filmers look forward to the screening season. SELECTING THE SCREEN SURFACE Probably the first decision the projectionist ought to make is what kind of screen surface he wants to use. Speaking generally, and without using trade names of one product or another, there are three major kinds of screen surfaces being offered today. These are (1) the glass beaded; (2) the matte white, and (3) the silvered surface. Which one of these surfaces you select will depend almost entirely on the uses to which you intend putting it. A projection surface has two major qualities by which it may be evaluated. One is its relative brightness, or ability to reflect the projected light and image. The other is its relative diffusion of the light and image projected on it. This latter quality largely determines at how wide an angle from the projection axis a given screen can maintain an adequate amount of its total brightness. Broadly speaking, it should be obvious that the higher the relative brightness of your screen surface the more desirable it will be. This is increasingly true when your projection involves color film, a low wattage projector or the necessity for a large screen. Maximum screen brightness, however, is not a fixed quantity nor is it the only factor which should be considered in your screen selection. BRIGHTNESS VARIES WITH ANGLE For it will be seen in Fig. 1 that the relative brightness of all screen surfaces varies with the angle from which they are viewed. It is here that the relative diffusion ability of a screen begins to have its effect; for it is this quality which determines how much or how little a screen surface falls off in relative brightness as the angle of view increases. Fig. 1 shows clearly the basic ratio between the beaded surface and the matte surface in these two qualities. The beaded surface, when it can be viewed from any position within a twenty degree angle on each side of the projection axis, has a relative brightness which exceeds that of the matte screen. When viewed within a ten degree area, the beaded surface is markedly more brilliant than the matte type. At the same time, it should be noted that a beaded screen falls off in reflective ability at a faster rate than does the matte screen. This is because of the highly directional quality of the beaded screen and its consequent inability to diffuse the image evenly in all directions. From these data, the amateur filmer can draw certain conclusions. If his screening arrangements (at home or in