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achieving this to a high degree of accuracy. It is also necessary, although not difficult, to balance very exactly the exposure produced in each gate aperture so that 12.5-cycle flicker is avoided. The reproduction of movement is
theoretically worse than with an ideal 25-frame television-recording system. However, tests have shown that, in fact, movement is reproduced very satisfactorily and compares with normal motion pictures.
(a;
(c)
(f) (9)
Fig. 6. Diagram illustrating the effect of picture joins.
(a), (b) and (c) show the effect of the shutter opening.
(d) shows the lines recorded during the last scan.
(e) shows the picture join obtained.
(f), (g) and (h) illustrate the fading-shutter method.
(4) SOME FACTORS AFFECTING THE PERFORMANCE OF TELEVISIONRECORDING CAMERAS
(4.1) Picture Joins
In the American system of television recording and in the 16| or KempDuddington systems, when used in a general phase relationship, picture joins occur in the picture area. With a cathode-ray-tube phosphor of negligible afterglow and using a focal-plane shutter, the sequence of operation is shown hi
Fig. 6. As the shutter opens after the pull-down period, lines should be recorded of increasing length owing to the diminution of the occulting effect of the shutter edge. This is shown in Figs. 6 (a), 6(b) and 6(c). For the next scan the shutter is open, and in the last part of the cycle the lines should be recorded of decreasing length and in such a position as exactly to join with those recorded
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April 1953 Journal of the SMPTE Vol.60