Motion Picture News (Nov-Dec 1923)

December i , 1923 2603 NEW THEATRE Construction & Equipment projection department P. M. ABBOTT CAMERA TECHNICAL EDITOR Correct Screen Necessary for Good Pictures Types Recommended for Individual Theatre; Also Maintenance of Reflecting Surfaces THE screen is a very material factor in good motion picture projection. The size and shape of house and its purpose, whether used as a motion picture theatre exclusively, for motion picture and vaudeville, or for educational pictures; the location of seats and projection room; and type of projectors used, all have a very important bearing on size, surface, finish and location of the screen which will produce the most satisfactory results. The material of which the screen is made may consist of one of several different kinds of cloth, or rubber composition, or of a plaster or similar smooth wall. The cloths most commonly used are canvas, muslin, sateen and linen. Linen is rapidly going out of use for the purpose in question on account of its cost. Untreated white cloth or white paint with a flat or non-glossy surface will give a reflected light distribution similar to the commercial diffusing screen, see Figure 170 (next page). Glossy cloth will show a distribution curve intermediate between those of the diffusing and metallic screens. However, the use of untreated cloth is most unsatisfactory as such a screen is extremely inefficient, all the light which passes directly through the weave of the cloth being lost entirely. Mounting the Screen A good method of mounting the screen is to stretch it tightly on a strong wooden frame, such that there is no cracking or peeling of the screen due to bending, and any wrinkles which might appear can be removed by adjustment of the stretching devices. Particularly in high school auditoriums, churches and other locations where performances are held infrequently, it is necessary that the screen be rolled up when not actually used for the projection of pictures, and this without any danger of cracking or peeling. Some very good screens are quite flexibly constructed. One method of accomplishing this result is to use on the cloth or other base a paint which is composed of a white pigment mixed with ordinary rubber cement or a liquid adhesive which has similar properties. Frequently, the screen is painted directly on the wall of the theatre, the latter being of plaster or cement. If the plaster wall is properly treated with the same kind A GOOD screen is a most essential element for successful presentation of motion pictures. By a "good" screen is meant a screen that embodies the correct physical characteristics which make it especially adaptable to the particular theatre. Each theatre presents its own problem in the selection of the screen best suitable for giving a brightly and evenly illuminated picture to the great majority of seats in the house. No one type of screen best serves all theatres. A long narrow house using a highly diffusing type screen requires as much light projected to the screen as though the theatre was of great width. A narrow theatre can make good use of a reflecting type screen. A theatre which has a broad dimension if employing a reflector type screen is presenting a dark and unsatisfactory appearing picture to a large portion of the seats in the extreme sides of the house. A diffusing type screen is required. The houses between the narrow and broad types should install a screen with characteristics of both the reflector and diffusing types. Study the screen problem in your theatre. Often the screen proves to be the seat of projection troubles. Keeping the screen surface free from dirt and replacing the screen when the reflecting surface is deteriorated is of utmost importance. Valuable suggestions on the selection and maintenance of screen surfaces are giving in the second excerpt of the Westinghouse Lamp Co. bulletin "Motion Picture and Stereopticon Projection with Mazda Lamps," presented on this page. Fig. 171 — Three typical motion picture screens. and diffusing Left to right: beaded, metallic of material as is used in the construction of a high grade commercial screen, this method should produce a good picture background. However, frequently a mediocre paint is used, producing inferior results; furthermore, immobility is often a disadvantage. Where the screen is painted on plaster applied directly on the inner surface of one of the outer walls of the theatre, trouble is often encountered, due to the dampness of the walls. A fairly heavy rain on a brick wall or a sudden change of temperature will cause moisture to seep through or condense on the front surface of the screen, resulting in an extremely blotched and undesirable appearance. Such a difficulty can be overcome to a certain extent by waterproofing the brick wall, but the most satisfactory remedy is to install a commercial screen separately mounted a short distance from the wall. Reflecting Surfaces Screens may be classified according to their surfaces, as diffusing, metallic or beaded, see Figure 171. The difference in light reflecting properties of these three types of screens may be seen from the reflection curves of Figure 170. The diffusing screen, of which the flat matt plaster is the most common example, reflects the light to about the same extent in all directions. With this surface, at whatever angle the picture is viewed, the brightness is practically the same. The curve of the metallic screen, on the other hand, shows a very high value of rer fleeted light directly in front of the screen which decreases rapidly as the spectator moves to the side. The beaded screen shows a curve more closely approximating that of the metallic. This screen is composed of a large number of minute glass beads mounted on a flat background, the beads forming innumerable small light reflecting surfaces. In a number of cases a blue tint is added to an otherwise flat white screen in the attempt to give the picture an appearance more nearly pure white. Except in cases where an extremely faint tint is used, this practice should be discouraged in motion picture projection unless the source of light is much stronger than is needed. While a noticeable tint of blue will give the effect of a white picture to a certain extent, it will ap