Theatre Catalog (1954-55)

Effects of Stray Light on Picture Quality” A Comprehensive Study of the Influence of Stray Light on The Quality of Indoor and of Drive-In Projected Pictures Whenever pictures are projected on a screen, the brightness range of the screen image from highlight to shadow is established by two limits: First — The brightness limit for the highlight is controlled by the light output of the projector in combination with the size and reflection qualities of the screen. Second — The limit of darkness is established for any projection screen by its stray-light level. The deep shadow region in the screen image may approach, but certainly cannot be darker than, this lower limit set by the stray-light level. In one form or another, it is generally recognized that stray light is a problem. Four instances of this are: 1. A U. S. Navy technician has said, “When a full Bermuda moon rises to flood out our outdoor screen at Hamilton, we’re in trouble. Such moons were obviously made for romance and not for the showing of open-air movies.” 2. The Committee on Non-Theatrical Equipment of the SMPE in 1941 reported, “Good Tonal Quality in the *Most of this article has been taken from a paper on the same subject which appeared in the Journal of SMPTE, Volume 61, Part I], pp. 257-272, August, 1953, through special permission granted by the Editor. 1954-55 THEATRE CATALOG By Raymonp L. Estes Eastman Kodak Company Film Testing Division projected picture is impossible if the room in which it is being viewed is not adequately darkened.’”” 3. The National Educational Association stated in a recent audio-visual publication, “Light Control is one of the most important of the special problems facing school planners who are designing classrooms to meet the needs of modern education.”* 4. A projectionist at a neighborhood theatre recently stated that they were forced to raise the level of illumination in their auditorium in order to prevent rowdyism. Therefore, wherever pictures are projected, stray light may become a problem, be it classroom, drive-in, or theatre screen. STRAY LIGHT For the purpose of this paper, stray light is defined as the brightness in footlamberts (ft-L) produced on a projection screen by any unwanted, non-image IT IS IMPORTANT that fine theatres, such as the Fairmont, Cleveland, preserve the quality of the picture shown, by controlling stray light factors. 3 a. > . < me 4 a BRIEF: Whenever stray light causes a severe loss in the brilliance . . . beauty . -. and detail of a projected picture... unfavorable audience reaction can be expected—whether it be in regular or drive-in theatres . . . auditoriums .. .or classrooms . .. A study of the basic effects of stray light and their relation to picture quality is discussed in this paper ... together with methods of controlling the important factors involved ... In addition . . . results of a special screenbrightness and _ stray-light survey of drive-in and regular theatres in Rochester are presented ... These data emphasize that stray light is most serious ichen screen brightness is below standard .. . In this situation, the harmful effects can be minimized by increasing the level of screen brightness; usually this can be accomplished by precise adjustment and careful maintenance of the equipment. forming illumination that may be superimposed upon the projection screen image. Therefore, the maximum possible tonal range for any screen image from highlight to shadow will be contained between these two limits: the screen brightness and the stray-light brightness. Generally speaking, the greater 275