Amateur Cine World (June 1935)

New N a few. months’ Je: a wonderful new 16mm. colour film, Kodachrome, is to be launched on the market by Messrs. Kodak, Ltd. It is the invention of Mr. Leopold Mannes and Mr. Leo Godowsky, two young musicians, who have colour photography for their hobby. The fidelity of the colour rendering in the reel shown to us is remarkable. The flesh tints in the close-ups were admirably reproduced ; the colouring is balanced, no one colour being predominant. The transparency and clarity are particularly notable. It owes this in part to the fact that there isno grain. There is also no fringing. The colours look natural; there is no harshness about them and the colouring of the distant objects was as faithfully reproduced as those of near ones. No colour filters, either for camera or projector are necessary. The film is used in the camera in exactly the same way as ordinary black and white stock and is, indeed, nearly as fast as ordinary panchromatic film. It can thus be used in any spool-loading camera with an f/3.5 lens as well as in cameras with faster lenses. As a guide to exposures, one stop larger than for the same scene taken with ordinary pan is used. As an instance, if black and white pictures with ordinary pan are taken at f/11, then the correct stop for Kodachrome for the same scenes is one larger—namely, £/8. Fidelity of Colouring : We were extremely impressed with the reel we saw, both on account of the fidelity of the colouring and the ease with which the results were obtained. As to its latitude and consistency we are, of course, unable to judge until we have an opportunity of testing the film. This particular reel is the only one at present in this country, but the film will be available to all 16mm..-users as soon as the processing machines are installed in this country. The projector used for the demonstration was fitted with a 500 watt lamp, but we are informed that admirable results were obtained with only 100 watts illumination. The price of Kodachrome will be the same as that of Kodacolor—21/for a soft. reel. The film is produced by what is known as the subtractive process, as distinguished from the additive process. ‘The separation of light into three components is accomplished by coating the film no fewer than five times. The coatings are :— Beet SE: No Filters Reguired. RAW FILM BLUE SENSITIVE EMULSION GREEN a A RED 7 ANTIHALATION BACKING Entire Process. ‘___ocnmummammmms, MAGENTA IMAGE CROSS-SECTION OF KODACHROME FILM 16mm. COLOUR “sia Kodachrome—A Wonderful ; No. 1 (on the base Achievement. Ge aie ee ae Full Details of the emulsion which is strongly red-sensitive. No.2. -A: layer of gelatine containing some dye to act as a filter. No. 3. A coating of green-sensitive emulsion. No. 4. Another separating layer. Ce No. 5 (the top coat)—A_ blue-sensitive emulsion which contains a certain amount of yellow dye. In preparing the pictures for projection the film undergoes special treatment involving the use of three separate machines. The film itself is panchromatic and bears the ordinary jet backing as used on regular Cine Kodak film: The emulsion, however, consists of three layers each sensitized to one of the primary colours and separated from the adjacent layer by a thin coating of clear gelatine. The top layer of emulsion on which the light first falls in exposure is sensitive only to blue light, but it does transmit green and red light to the layers underneath: While it 1s sensitive to the blue it also contains a yellow dye which keeps the blue light from passing on through to the silver bromide grains below. The second or middle layer is sensitive to green and blue light, but as all blue is filtered out by the yellow dye just mentioned, we need to consider only its reaction to the green. Next to the film support is the bottom or third emulsion, which is sensitive to red and blue, but here again the blue being stopped in the surface layer, this emulsion reacts to red only. Briefly, there are three. separate emulsions sensitized as follows, the first or top layer to blue, second to green, and the third or bottom to red light. Each of these coatings is exceedingly thin so that their total thickness is about the same as the thickness of Cine Kodak emulsion. Kodachrome film is exposed in the normal manner, that is, with the emulsion side toward the lens. It is unnecessary for the light to pass through the support as it does in Kodacolor or any of the colour screen processes. THE SUBTRACTIVE PROCESS—AN EXPLANATION. Colour processes are generally divided into two types, the additive and the subtractive. With the additive process the actual red, green and blue colours are either visible in the film itself or are formed by an optical (Continued on page 130) COLOR POSITIVE __-YELLOW IMAGE BLUE-GREEN IMAGE SAFETY FILM SUPPORT 114