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Film Projection Using Image-Orthicon Cameras
By R. D. GHIPP
Presented here are the results of over a year's use of image-orthicon cameras for all film transmitted by television station WABD, New York, totaling approximately 2000 hr. In addition to brief consideration of the technical problems encountered, cost, reliability, convenience and other operational factors are discussed.
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VER THE PAST two years there have been a number of discussions concerning the use of the image-orthicon pickup tubes for the transmission of film.1"3 These have covered, in some detail, the characteristics of such tubes, and the basic design of film projectors for television. They have also suggested some of the advantages and the disadvantages of film cameras using image orthicons. The Research Division of the Allen B. Du Mont Laboratories, Inc. commenced tests of this type of pickup in 1948. By early 1950 image-orthicon techniques were such that practical operating tests were in order. WABD in New York then installed one unit. The results led us to conclude that, for the broadcasting of "run-of-the-mill" available film, often without system preview or rehearsal, the image-orthicon camera had several desirable features. By early 1951, WABD was using Type 5820 Image Orthicons for all film transmission. It
Presented on October 6, 1952, at the Society's Convention at Washington, D.G., by R. D. Ghipp, Director of Engineering, Du Mont Television Network, 515 Madison Ave., New York 22, N.Y.
should be emphasized that we were primarily concerned with consistently good reproduction of films of uncertain vintage and quality, rather than with excellent reproduction of a few films especially made and processed foi television.
Projectors
The WABD projection room was originally laid out in March 1946, and equipped with two Simplex 35mm and one Victor 16mm projectors. These had been modified for 2-3-2-3 pulldown. In 1948 we added two Du MontHolmes, Model 5130G, 16mm television projectors. These were placed and mounted as shown in Fig. 1 . Mounting details for the 16mm projectors, which weigh approximately 300 Ib, are shown in Fig. 2. The concrete base weighs approximately 500 Ib and provides extremely steady operation. Tests for picture stability are better than the proposed RTMA/SMPTE specifications, and no mechanical changes have been necessary to adapt any of the projectors to image-orthicon use.
Cameras
The cameras are standard Du Mont equipment, Model TA-124, normally
January 1953 Journal of the SMPTE Vol. 60