American cinematographer (Jan-Dec 1931)

l_ABCEATCEy and Technical Mattecc Screen Brightness THE QUESTION of screen brightness has arisen on many occasions but there seems to be very little definite data available as to what brightness should be maintained on motion picture screens. A review of the literature failed to show any definite recommendation of specific brightness values for motion picture films but it may be inferred from the experimental data in various articles published that an optimum value of screen brightness about eight years ago was 10 foot-candles. During the past year the Academy of Motion Picture Arts and Sciences has had a committee in operation called the Screen Illumination Committee, whose purpose it was to study screen brightness. The Society of Motion Picture Engineers for years had had a Theatre Lighting Committee, part of whose work was a study of the screen brightness subject. by EMERY HUSE, A. S. C. For a long time we have felt that a special department devoted to laboratory and other technical problems would be a feature that would be welcomed by the readers of this magaxine. Starting with this issue we are pleased to announce that such a department is now at your disposal, and is conducted by Mr. Emery Huse, A. S. C, technical editor of the American Cinematographer. Mr. Huse, whose picture appears at the left, needs no introduction, for his work with the Eastman Kodak Company has stamped him as a recognized authority. If you have any problems, send them into this department and they w'll be answered. — The Editor. There are occasions arising where a picture shown in two different projection rooms, or theatres, will look quite different on the screen. Reference is made particularly to the same print. Oftentimes as a result of the difference, blame is placed on the projectionist or on the laboratory for their print quality. In most instances the cause of this difficulty can be centered in the inequality of the brightness of the screens on which the picture is viewed. This general problem of screen brightness is of great magnitude and extends from the processing laboratory through the studio projection rooms to the screens of the multitude of theatres throughout the country. It is naturally quite impossible at this time to make a standard condition which would please all parties concerned but it does seem that at least within a given studio the various projection rooms could be maintained at some definite screen brightness. Furthermore, in making a study of various theatres and studios relative to their screen brightness the values are not greatly in disagreement but they are sufficiently so to make standardization impossible. Theatres agree among themselves fairly well, but the studios are not as good in this respect. The purpose of this article is simply to bring to the attention of those interested a tabulation of some of the data available at the present moment, which data was accumulated during the past year. The accompanying table gives rather completely such data. Color Coefficient THE SENSITOMETRIC term "color coefficient" has been brought into the motion picture vocabulary since the introduction of sound photography. An attempt will be made here to briefly explain its significance. Screen Illumination Data For Several Los Angeles Theatres THEATRE TYPE LENGTH OF THROW TYPE OF SCREEN SIZE OF SCREEN SCREEN ILLUMINATION FOOT-CANDLES A Neighborhood 100 ft. Transvox 13' 2" x 17' 8" 8.5 f. c B " 99 ft. " 13' 2" x 17' 8" 10 f. c. C L. A. Class A 100 ft. Datone X 14' 3" x 19' 10.5 f. c. House D Hollywood Class A 95 ft. Transvox 1 8' 6" x 24' 7" 1 1 f. c. E Hollywood Class A 75 ft. 1 4' 6" x 1 9' 4" 12 f. c. F Neighborhood 125 ft. " 13' x 17' 5" 9 f. c. C Laboratory 65 ft. Datone X Exact dimension unknown 12 f. c. H " 35 ft. Not sound screen " " 24 f. c. 1 " 45 ft. Datone X 10x12 17 f. c. J 35 ft. Not sound screen matte surface 7 x 9'/2 38 f. c.