International projectionist (Jan-Dec 1936)

THE KELLER-DORIAN, THREE-COLOR MOTION PICTURE PROCESS Data Bearing Particularly Upon Projection Requisites of K-D Prints By WILLIAM E. CELESTIN PRESIDENT, THE KELLER-DORIAN COLORFILM COMPANY FOR the past two years representatives of Paramount, Eastman Kodak Co. and Keller-Dorian have been at work completing the final practical tests of a new and amazingly simple three-color process. Working under actual studio conditions, the process has demonstrated its complete applicability to modern production requirements, and established a new standard of fidelity, simplicity and economy. The Keller-Dorian process is by no means a mushroom growth. It was invented in France more than a decade and a half ago, and for the past seven years a somewhat crude version of the process has been in general use in the 16 mm. field under the trade-name "Kodacolor" ("Agfacolor" in Europe). Millions of feet of successful 16 mm. color have been made in this process by unskilled home-movie makers. Thus the task has been one of refining and adapting a commercially successful process to the requirements of present-day studio production. This work has reached fruition in a three-color additive process which permits the use of any standard black-andwhite camera with minor optical modifications and using but a single film. The processing is familiar black-andwhite technique, and can be carried out in any plant; no centralized "color laboratory" is required. Experts have pronounced the screened results more tiue-to-life than anything yet seen; and the cost-sheets prove the process the most economical three-color system yet introduced. In any three-color process, it is necessary to secure three color-separation images, one of which records the red components of the scene, another the blue, and the third the green. In some processes, these separations are obtained by using three separate films; in others, the three images, either as three normalsize frames or three frames of reduced dimensions, have been made on one film through intricate beam-splitters and prisms. In the Keller-Dorian process, a unique yet essentially simple optical system combines these three separations in a frame which is to all appearances a perfectly normal single image. The celluloid base of the film is embossed to form a myriad of tiny cylindrical lenses which extend from one side of the frame to the other. A special filter consisting of parallel horizontal strips of red, blue and green is placed on the camera lens. Each of the tiny embossed lens-strips on the film forms a microscopic image of this filter on the emulsion; therefore each frame consists of an infinite number of parallel, microscopic strips, each of which is photographed through one of the primary-color filter areas of the lens. Projection Requisites The same principle is used in projection, with a suitable three-color filter applied to the projector's lens. Thus in photographing a red object, for example, the red rays could pass only through that part of the lens governed by the red section of the filter, and would be arrested by the blue and green sectors. A Note Anent K-D Projector Optical Setup MANY a projectionist eyebrow will lift upon reading in the accompanying article of the new optical setup developed for the projection of Keller-Dorian color prints whereby an increase of 380% in illumination is reputedly obtained. Projectionists will immediately conclude — and rightly — that such a combination would be worth its weight in gold and provide the answer to many projection problems other than color reproduction. The combination referred to in this article consisted of an f/1.9 lens and an f/1 condenser— a grand piece of optical work and a beautiful setup, indeed. When installed in a high-intensity lamp pulling 125 amperes — the distance between the combination and the carbon crater necessarily being short — this combination literallyburned up. The crater being so close, the heat was terrific and the pitting extreme. As fast as the optical people made up the combinations the projectionists broke them. What improvement, if any, has been effected is not known; but in the light of claims made for this setup this clarifying statement seems unwarranted. — Editor. [24] This condition would be passed on to the emulsion through the lenticulations on the film-base: the red-filtered strips only would receive exposure. In the developed negative, only these red strips would be dense; the adjacent blue and green filtered strips would be clear. In the print, these latter two strips would be opaque, while the red-filtered strip would be clear. When projecting, the light from the lamp would pass only through the clear, red-filtered section; and the embossed lens on the film would guide it to the red-filter section of the projecting-lens, reproducing the image of that part of the picture with red light. The coloring is thus produced and reproduced solely by the familiar factors of filtering and black-and-white density. Since these are so well understood from years of monochrome experience, there is no factor which can cause color-variation in the release-prints. Any standard camera suitable for serious black-and-white cinematography can be used as a Keller-Dorian color camera. At present, the studio-type Akeley is preferred because of the advantage its 230-degree shutter offers in offsetting the light-absorption losses of the tricolor filter. The lens used is of special design, to coordinate with the film base lenticulations. It is of the convertible type, and works at f/1.9. A fixed front element is used in conjunction with a variety of interchangeable rear elements, which give a wide range of focal lengths. The filter is mounted at the center of the lens, and a supplementary optical unit is installed directly before the photographing aperture to eliminate colorfringes in the out-of-focus parts of the picture. Due to the nature of the process, the reversal process is used rather than the conventional negative-positive system. This method is well understood, and introduces no complications. Standard developing machines can be converted to reversal-processing with only minor modifications. As the film exposed in the camera is reversed into a positive,