Transactions of the Society of Motion Picture Engineers (1916)

white records may or may not exist, depending on whether the films are constructed on the additive or subtractive methods. Each alternate image area may vary in its colors so that the fullest color rendering is only obtained on projecting. For example, each alternate color-image may be a representation of the Reds and Greens, while the second set of alternating images may be a record of the Orange-Yellows and Blue-Violets. The colors fuse or combine when projected. We are nearer to a successful realization of this form of color film than many of you are aware, and it may be of interest to point out a few of the suggested or attained methods. (a) Single Coaled Emu/sion.Two or three-color images are impressed in the gelatine. Usually one of the color-images is the result of the silver in the original emulsion, with the second color-image obtained by means of a sensitive bichromate salt. If a third color-image is to be impressed into the emulsion in register with the first two, it may be applied by imbibition. It is quite possible to get the two colors in the single emulsion. I have done so, in projectionable lengths. There are certain obvious drawbacks, however, from a commercial aspect. (^) Two Emulsions on One Side. The first color-image may be a blue tone in the original coating. A second emulsion is then coated over the first one, printed, and the silver converted to a red color by toning or otherwise. I have seen reels of film produced by this method that appeared to be satisfactory, but I understand that there are manufacturing difficulties. It always seemed as though it was too long a wait, after finishing the first color-image, sending the film back to a red lighted coating room for a new coating, a new printing and development and a second coloring before determining if everything had gone right on the first tone. Not to speak of the added difficulties of registration due to alteration in length, the expense of making short lengths and so on. (The Fox system follows this procedure.) {c) Double Coated Emulsion. Here we have a celluloid base with a silver emulsion on each side. Both sides are printed before development. If on a two-color basis, all of the red value pictures are printed on one side and all of the green value pictures on the opposite side in register, and after development the black images are converted or transposed into color-images. This process is "healthy" and will, doubtless, be the first to reach the market in some form or other. {d) Single Coated Emulsion. The celluloid base is colored in fine dots or lines. In one method published, the celluloid is passed over suitably engraved rollers and fine ridges impressed in the base forming hollow spaces, similar to the raised portions on the opposite side. These depressions are filled with colored inks, red on one side and green-blue on the other. Variations provide for 3 and 4 colors. The emulsion must be color sensitive and the negative printed with colored lights or their equivalent. (See Dufay U. S. Patent No. 1,15^,900.) Some other developments are not far enough advanced for me to give you a description now Those described will serve to show you the general direction of the work. Many of these and similar ideas were discussed or described seven or eight years ago, but the difficulties of 39