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Kinescope Recording Film Exposure Control
Bv RALPH E. LOVELL and ROBERT M. ERASER
Various devices have been perfected to control accurately the exposure of video pictures to be recorded on motion picture film. These devices, combined with sensitometric control, take much of the guesswork out of the kinescope recording process.
M,
.UCH HAS BEEN WRITTEN about the
various phases of recording television images on motion picture film. Equipment has been described, characteristic curves of the various components have been examined, and questions of resolution have been discussed. Little material is available, however, about the methods by which proper film exposure can be obtained from a kinescope tube.
It is the purpose of this paper to describe a practical operating procedure for obtaining optimum film exposure on kinescope recording negatives. This is a technique involving the use of some instruments well known in connection with electronic applications as well as others designed specifically for the purpose.
One of the many handicaps under
Presented on October 7, 1952, at the Society's Conventional Washington, D.C., by Ralph E. Lovell, National Broadcasting Co., Sunset and Vine, Hollywood 28, Calif., who read the paper, and Robert M. Eraser, National Broadcasting Co., 30 Rockefeller Plaza, New York 20, N.Y.
which the technician worked in the early days of video recording was the lack of suitable instruments for determining conditions of film exposure. The early commercial kinephoto monitors had, as their sole instrument for determining the effects of changes in contrast, brightness and high voltage, a single 50-jua meter, which by selective switching was supposed to indicate conditions in various circuits. The only method of judging maximum exposure conditions with this apparatus was to observe the average cathode current of the 5WP11 recording kinescope. A rough approximation of minimum exposure conditions — referred to as black level — could be obtained by an indication of the grid bias voltage of the 5WP11 kinescope. With this crude method of instrumentation the technician was supposed to maintain uniform exposure and produce good photographic results. Needless to say, this was an almost impossible task.
The situation today at NBC is quite different. Several instruments have
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March 1953 Journal of the SMPTE Vol. 60