American cinematographer (Jan-Dec 1931)

Television in Color from Motion Picture Film by HERBERT E. IVES Bell Telephone Laboratories, New York. IN SPECULATIONS on the possible uses for television, one project which receives considerable attention, partly because of its relative ease of accomplishment, is the transmission of images from motion picture film. It is true that the practical simultaneity of event and viewing, which is the unique offering of television, is lost when the time necessary for photographic development of the film intervenes. Nevertheless it is conceivable that if this delay is small, television from film may still possess such an advantage over the material transportation of film as to give it a real field. A further possibility, more remote, but within the range of legitimate speculation, is that television apparatus may sometime be used to receive, in the home, motion pictures of the sort now offered in the theatres or in home projection outfits. However distant these mergings of the two arts may be, the technical problems presented are pretty clearly defined, and offer interesting features for study. Among these problems is the transmission of images in color from colored motion picture film. This paper describes a method of accomplishing this, using the receiving apparatus for television in color recently described, and special sending apparatus which utilizes the latest form of colored moving pictures — the ridged film now marketed under the name of Kodacolor. As an introduction to the method of telecinematography in color using ridged film, it is profitable to outline how the problem could be solved with film in which the colors are incorporated by dyes (e. g., Technicolor) , and the three-color transmitting and receiving system recently developed in the Bell Laboratories.1 This may be done most easily by considering Fig. 1, where the three-color transmitting apparatus is shown in section, with the addition of film handling means. The Fig. 1 photoelectric cell cabinet, containing three sets of color-sensitive cells with appropriate filters, is indicated at C, from which three communication channels, R, C, and B, carry the red, green, and blue signals to the receiving end. At A is the arc lamp, whose light is condensed upon the perforated disk D, which is driven by the synchronous motor M. The lens L projects an image of the disk upon the matte white screen S, from which light is reflected back into the photoelectric cells. The film F, as it unwinds from the reel Ri onto the reel R passes in front of the disk D, and as closely as is practicable to it so that the film and the disk holes are in focus together on S. If, with the apparatus as just described, the film stands still, with a picture frame exactly filling the field aperture in front of the disk, and the disk rotates at its normal speed for television, the screen S shows a projected image of the film, colored if the film is colored, and capable of being picked up by the photoelectric cells and transmitted, to be received like the image of a colored object by the single disk, three-lamp receiving apparatus, as ordinarily used for this purpose. When the film is moved in order to give a motion picture, there are two alternative forms of scanning disk available, depending on whether the motion of the film is intermittent, as in most cameras and projectors, or continuous. In the first case, a scanning disk must be used with a blank sector corresponding to the period occupied by the shift of the film between frames, as shown in Di, Fig. 2, and a similar disk must be used at the Fig. 2 receiving end also. The use of intermittent exposures is, however, not only inefficient, because of the waste of line-time during the blank period, but is quite unnecessary when the image is analyzed by successive passages of a scanning aperture across the field. Instead of a disk provided with a spiral of holes it is simpler and better to use a disk with the scanning holes arranged in a circle, as shown at D2, Fig. 2, and to give the film a uniform and continuous motion along the vertical diameter of the disk. When this is done the screen S shows merely a horizontal strip of light (indicated in Fig. 1 by the solid line) but the usual spirally-perforated disk at the receiving end spreads this out into a complete picture. This method of transmitting colored images from motion picture film, while completely practical, suffers under the disadvantage that it requires an original colored film of a sort which is both expensive and time-consuming to produce. Should television transmission from film become popular it is probable that the chief demand would be for films which would be shown but once, and for showings within a few hours, at most, of the event. Some form of colored film would then be called for which could be prepared quickly and cheaply, and the film process need not be one adapted for making numerous copies. A form of colored motion picture which very completely meets these requirements is produced by the Kodacolor process." In this the image is black and white, but is distributed into a triple linear mosaic by lenticular ridges on the film. Exposure is made through a lens with three apertures, and pro 16