Journal of the Society of Motion Picture Engineers (1930-1949)

the television camera, where strobing can take place between the line scanning and objects moving up or down the vertical axis of the picture. Tilting of the camera can produce the same effect. It must be noted that in the recording of a television picture strobing effects are confined to the electronic pick-up camera and do not occur at the photographing point, because the photographic camera has a fixed viewpoint. Nevertheless, even in its reduced form, the result of "line crawl" introduced by the camera can be quite serious. Thirdly, the use of interlacing gives rise to a particularly objectionable form of movement blur, because two discrete and separate images of a fast-moving object appear on the screen, displaced from one another by the distance through which the object has moved in the ^g-sec interval between the writing of the two superimposed rasters. This is a form of movement blur which finds no counterpart in the natural response of the eye or in normal cinematography. On the question of recording television images on film, however, it will be immediately apparent that the need for interlacing fundamentally does not exist, because the standard picture repetition rate is 24 frames/sec, elimination of flicker being effected at the film projector, where the light is obdurated twice, or preferably three times, during the projection of each picture frame. Freedom to use sequential scanning leads to a consideration of its advantages, which may be stated as follows : (a) It is appreciably easier to obtain accurate registration of the lines in a sequential than in an interlaced raster. (b) Movement blur, due to the formation of double images, and line crawl are eliminated. (c) The obligation to produce an exact number of lines per frame no longer exists, which opens up possibilities of the introduction of advantageous effects analogous to the dynamic-definition effect. (d) The number of frame-suppression periods per picture is reduced from two to one, thus materially increasing the "time efficiency" of the system. It is thus suggested that sequential scanning presents so many advantages that its use is to be preferred. The serious disadvantage lies in the fact that the pictures viewed by eye, during production, suffer from the severe disadvantage of 24-cycle/sec flicker. There seems some hope, however, that the effect of flicker may be to a large extent reduced by the use of reproducing cathode-ray-tube screens having long decay times. (5) The Electronic Camera (5.7) Brief Description of System: To summarize the foregoing, it would appear that the use of a 1,000 to 1,300line sequentially-scanned electronic image with a bandwidth of 1 5 to 20 me will suffice to give adequate definition for the production of acceptable motionpicture film, provided that the whole system is sufficiently free from loss and distortion. The contention is advanced that definition of this order is within range of modern electronic equipment and that, within a short time, equipment which has been developed in the laboratory will be available in a form which will be suitable for use on the studio floor. (5.2) Optical Performance: No limitation in definition is imposed on the system by the taking lens of the electronic camera, since good-quality 35mm lenses of to-day are capable at full aperture of resolving from 8 to 10 times the fineness of detail normally required for making a film optically. The use of a standard range of 35mm lenses also ensures that depth of focus, taking angles and so on, are exactly similar to those to which film technicians are accustomed. Handling Characteristics: Electronic cameras can be made in conventional shape, but much smaller and 454 December 1952 Journal of the SMPTE Vol. 59