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

*(3) SYSTEMS OF TELEVISION RECORDING These can be divided into two groups : those in which the film moves continuously, and those in which the film moves intermittently as in normal motion picture practice. (3.1) Continuous-Motion Types To record interlaced television by this method, the geometrical displacement error over the extremes of movement must be less than one picture element, in both line and frame directions. (3.7.7) Cameras Employing Picture Movement: In this system, the television picture on the cathode-ray-tube face is moved physically in such a direction that it remains stationary relative to the film, which is moving continuously at 25 frames/sec. The movement of the picture is achieved by electrical deflection of the raster. The high degree of precision to be attained has precluded the development of a practical television-recording system using this principle. (3.7.2) Cameras Employing a Picture of Special Aspect Ratio and Double Optical System: This is the normal method of transmitting film by means of the flyingspot principle, but used in reverse. The film moves continuously at 25 frames/sec and two images of the television picture, which is of approximately twice the normal aspect ratio, i.e. 8:3, are focused on the film, separated by half a film-frame pitch. The film moves half a frame pitch during the recording of the first field and this movement restores the aspect ratio on the film to the normal value. During this period the second image is obscured by a shutter. The shutter then obscures the first image and allows the second image to be exposed to the film, the lines * The section numbers in this abstract are not consecutive. The author's original section numbers have been retained for the sake of consistency in reference to the original paper. — Ed. falling between those of the first field, since the film has now moved to the required position. (3.7.3) Shutter less Cameras Employing Optical Compensation: There are numerous designs utilizing this principle. Most of them were intended for cinema projection where it was hoped to increase the screen brightness and reduce the flicker content, owing to the elimination of the shutter intervals. Despite the theoretical advantages of continuous-motion projectors, compared with those having intermittent motion, they have never proved popular in the motion picture industry, probably because of the complexity of the various designs. The Mechau projector, however, enjoyed moderate popularity in Germany and an improved version of this machine has been converted into a recording camera for B.B.C. use. Apart from the Mechau projector, only one other type of optical-compensation projector has been used to any extent; this is the type employing a thick polygonal prism. The system is extremely simple and involves a minimum of moving parts; for this reason it is the basis of most highspeed cameras, exposure rates of up to 3000 frames/sec being attainable. The difficulty for adaptation to television lies in the accuracy necessary in manufacturing the prism, the large size of the prism required for high definition and the problem of adjustment for film shrinkage. A telecine projector working on this system has, however, been built in the United States, and at least one home projector of similar design has been marketed in Germany. The Latest B.B.C. 35mm ContinuousMotion Recording System: The first B.B.C. 35mm recording suite went into service in October 1949. The design utilized the 368 April 1953 Journal of the SMPTE Vol. 60