International photographer (Jan-Dec 1935)

May, 1935 The INTERNATIONAL PHOTOGRAPHER Seventeen would be extremely expensive, whereas once the three negatives have been obtanied and a method of printing them has been worked out, the preparation of a large number of prints is not unduly costly. The new Kodachrome process is a subtractive process, but the separation of the light into the three components is not accomplished by placing the separate components in juxtaposition. They are separated in depth. The film for this process is coated no less than five times! Nearest the base, an emulsion is coated which is strongly red-sensitive. This is then over-coated with a separating layer of gelatin containing some dye to act as a filter. Above this is coated a green-sensitive emulsion. This is over-coated again with another separating layer. Finally, there is applied a top coat which is blue-sensitive and which contains a certain amount of yellow dye. The five coatings are so thin that the total thickness of the film is little more than that of ordinary-line Kodak film. The emulsions are so adjusted that the sensitizers do not wander from the layer in which they are coated, so that the bottom layer remains red-sensitive with very little green sensitivity, the middle layer is green-sensitive and is free from red sensitivity, while the top layer is sensitive only to the blue. When a picture is taken upon such a film, the three components are automatically separated in the depth of the coating. The red component is formed in the red-sensitive emulsion nearest to the base, the green component is formed in the middle layer of the emulsion, and the blue component forms the image of the top layer. In order to obtain a color picture with this film, all that is necessary is to transform each component image of the negative into a positive image consisting of a suitably-colored dye. The image formed in the red-sensitive (Continued on Page 20) la\er is transformed into a blue-green positive; the image formed in the middle green-sensitive layer, into a magenta positive ; and the one in the top blue-sensitive layer, into a yellow positive. This is accomplished by an extremely complex processing system. The images in the three layers are first developed, as with ordinary black and white film, and then by a series of treatments the images in the three layers are transformed into positives formed in the dye. The whole of the silver salts are removed finally, and the image consists of three superimposed dye pictures. The process is the invention of Mr. Leopold Mamies and Mr. Leo Godowsky, Jr. These gentlemen are musicians whose names were well known in the musical world when some years ago they commenced the study of color photography as a hobby. As a result of collaboration between them and the Kodak Research Laboratories for a number of years, it was evident that the work could only be brought to a successful conclusion by a full utilization of the research and manufacturing facilities available at Kodak Park. Here, there were available experts of many kinds: organic chemists, emulsion-makers, dye specialists, photographic chemists, and experts in photographic operations — and in 1931, therefore, Mr. Godowsky and Mr. Mannes joined the staff of the Research Laboratories. By the complete cooperation of the staff of the Laboratories and of the Kodak Park Works, a task which at first appeared impossible was achieved and the Kodachrome process is the result. The processing, as has been said, is extremely complicated and involves the treatment of the film upon three separate machines. Experience has shown, however, that it can be performed with certainty and that the commercial production of the color pictures presents little more difficulty than the production of black-and-white pictures, The Bell & Howell Cooke Varo Lens The Varo Lens is still an object of wonder in the studios where it is used . . . and in the cinema world at large as well. For among the most wanted things among the thousands of needs in cinematography has been a lens that would "zoom." The Cooke Varo Lens provides this magic. Write for full details. Sometimes available on rental to responsible studios. B & H Cooke Varo Lens in photographing position on the Bell & Howell Camera^ B &. H Cooke F 2 Speed Panchro Lenses B & H F 2 Speed Panchro Lenses, corrected for the blue and red rather than blue and yellow rays, are in use almost exclusively wherever successful cinematography is being turned out. Eleven focal lengths, 24 to 108 mm. B & H Cooke F 2.5 Panchro Lenses, at lower cost, meet many needs where such speed is adequate. Seven focal lengths, 35 to 162 mm. Write for prices. BELL & HOWELL COMPANY 1849 Larchmont Ave., Chicago; 11 West 42nd Street, New York; 716 North La Brea Ave., Hollywood; 320 Regent Street, London (B & H Co.. Ltd.). Est. 1907. Please mention The International Photographer when corresponding with advertisers.