International projectionist (Jan-Dec 1957)

at 7:00 p.m. Eastern time. It will have to be kinescope recorded in Chicago (6:00 p.m. Central time) for transmission 1 hour later; in Denver (5:00 p.m. Mountain time) for transmission 2 hours later, and in Los Angeles for rebroadcast 3 hours later. These and many other uses of kinescope recordings make them an integral part of any large television operation today, and it is conceivable that the value of color television recordings will be of even greater significance. Color Kinescope Recordings One of the easiest ways to make a color kinescope recording is to photograph a color TV picture using a multilayer color film. The film can be either a color reversal film, which will produce a color positive kinescope recording, or a non-reversal color film, which will produce a color negative kinescope recording. Interestingly enough, it makes little difference to the television system whether it "sees" a negative or a positive image, for by the simple flick of a switch, TV can make a positive image out of a negative image electronically. Good, highquality kinescope recordings of color television programs have been made on both 16-mm and 35-mm multilayer color motion picture films. These recordings are then reproduced by means of color film scanners. We mentioned earlier that the television industry was experimenting with additive color processes for color reproduction. These processes are especially interesting for kinescope recording not only because they use inexpensive black-and-white film which is quickly and simply processed, but also because additive processes are fundamentally more compatible with the color television system, which, as we have seen, is itself an additive color system. Briefly, an additive motion-picture color process involves photographing through red, green and blue filters to produce three black-and-white separation positives. These positives can be obtained by photographing three strips of film simultaneously, as in the three-strip camera. Or, by means of a special optical device, a red, a green and a blue image may be reduced in size and fitted into the approximate area of a single 35-mm frame. This latter system, of course, requires only one strip of film. In either case, separation positives may be made by ex A fortuitous accident(?) has developed what may be a large boon to exhibitors and projectionists; an optical track completely covered by a magnetic line may be played through with good quality and volume. Optical? Magnetic? Now Compatible MAGNETIC and optical soundtracks can be combined on one print and either track played at will through a revolutionary new procedure discovered by accident by George Lewin of the Army Signal Corps. It will no longer be necessary to use half-width tracks when optical and magnetic recordings are to be combined. Half-width tracks give poorer quality, and impose uneven head wear on magnetic reproducers. With this discovery, the same print can be circulated to theatres that are equipped and are not equipped for magnetic reproduction; and played in any theatre according to that theatre's equipment or the preference of its management or its projectionists. In nontheatrical applications the new process has obvious advantages in multi-lingual work, for example. The accidental discovery was made on a 16-mm print carrying a half-width optical recording and a half-width magnetic recording side by side. Through a fault in the striping machine the halfwidth magnetic track was misplaced and completely covered the optical re cording. None the less, when the film was played on a projector equipped for optical sound only, the optical track, covered and hidden by the overlying magnetic material, sounded fine! Lead-Sulfide Unit Used The projector used was a military model, embodying a lead-sulfide photoconductive cell in place of the more common, commercial caesium photoelectric cell. The lead sulfide unit is more sensitive to infra-red fight. The iron oxide magnetic stripe, which is perfectly opaque to the human eye and also opaque to a caesium cell, was found to be transparent to some frequencies of infra-red, and the lead sulfide cell was found to be highly sensitive to those same infra-red frequencies. The cell looks right through the iron oxide and sees the optical modulations. To adapt this procedure to theatre use the only projection room change, apparently, will be to substitute a photoconductive lead sulfide cell for the photoelectric caesium cell. posing onto black-and-white reversal film which yields the separation positives directly, or by exposing onto black-and-white negative film and printing separation positives. To reproduce the original color scene, these black-and-white positives are projected with red, green and blue light, and the light which passes through the three images is combined to yield an additive color reproduction. If the three-strip system is used, some means must be provided for registering the three strips exactly. With the single-strip system, the images are recombined by a special optical device similar to the one used during photography. The singlestrip system requires a dimensionally stable film, and produces on 35-mm film a picture which is less sharp than a 35-mm three-strip system. The fundamental reason for the difference in sharpness lies in the fact that, since all three records are reduced in size to fit into the approximate area of a 35-mm frame, we have in effect a 16mm rather than a 35-mm print. But because the television picture is small compared to a theatre picture, this difference in sharpness may not be significant. Lenticular Film A method of producing color motion pictures by means of a single strip of black-and-white film is the use of lenticular film. Novel, but by no means new, lenticular film is a single black-and-white emulsion coated on a base which has been embossed on the non-emulsion side with a structure of tiny half-cylinder-shaped lenses or "lenticules." These are placed across the film and have a radius of curvature of about 1/500 of an inch. This structure of lenticules presents an appearance much like a washboard with each individual lenticule acting as a miniature cylindrical supplementary lens. Lenticular film is exposed "backwards"— that is, through the base. The camera lens images a scene onto the lenticular structure of the base rather than directly onto the emulsion, as is usually the case. Each of the tiny len(Continued on page 27) 14 INTERNATIONAL PROJECTIONIST • JUNE 1957