Journal of the Society of Motion Picture and Television Engineers (1950-1954)

with relatively modest lighting requirements. Under these conditions, it was apparent that improvements were required in the film system to bring it up to the new standards of studio quality. The iconoscope camera, which has been almost universally used for film reproduction, was re-examined thoroughly and many improvements were made in circuits and operating techniques.1 These improvements have resulted in a substantial gain in picture quality and have been widely introduced into current film-reproducing equipment in television broadcasting stations. With high-quality film and careful operating techniques, the pictures compare favorably with those which originate in studios. However, within the last few years, there has been a definite trend in the direction of recording certain programs directly on film for reasons of smoother performance, possibilities of editing, less strain on actors and the increased versatility provided by the application of well-developed motion-picture techniques. Such a program is, therefore, no longer considered as a substitute for live-studio programs, but as a direct competitor. In this case, the ultimate goal is picture quality which will make it impossible for the home television viewer to know whether the program material is live or has been recorded on film. The same goal is called for in kinescope photography for delayed broadcast, program storage and distribution by network-affiliated stations. The formation of these new trends in television broadcasting spurred on an intensive program of evaluating many incompletely explored methods of film reproduction. Investigations showed that the vidicon pickup tube offers the greatest possibility for realizing these new objectives. Our work on the Vidicon Film Camera during the past two years has convinced us that it comes closest to meeting the requirements for an ideal film camera. Performance Requirements for a Television Film Camera Before describing the vidicon camera, it may be of interest to tabulate the main factors in any television reproducing system which are the criteria for good performance. These are: A. Resolution or aperture response. B. Available signal-to-noise ratio. C. Possibility of aperture-response correction. D. Gray-scale or transfer characteristic. E. Film-reproduction range and film latitude. F. Light-source requirements. G. Effect of spurious signals or shading. H. Black-level reference. I. Nonsynchronous projector operation. J. Possibilities for unattended operation. The vidicon tube was invented at RCA Laboratories2 and developed into a commercial product at the RCA Victor Tube Development Group at Lancaster.3 The capabilities and potentialities of the vidicon for high-quality film reproduction were first clearly recognized and demonstrated by R. G. Neuhauser of Lancaster. A detailed discussion of the theory and operation of this tube under film reproduction conditions is given by Neuhauser in the preceding paper in this Journal* We can most effectively evaluate vidicon performance by referring to the previously mentioned factors and reporting observations and measurements on these characteristics. A. Resolution: The 1-in. vidicon with a 0.62-in. picture diagonal (f X ^ in. picture) has a limiting television resolution of 800 lines in the center of the raster, with a measured response of 35% at 350 lines compared with zero line number as a base. B. The signal-to-noise ratio, measured as peak-to-peak signal to rms noise can be as high as 300 to 1. It is determined mainly by the shot noise 154 February 1954 Journal of the SMPTE Vol. 62