International photographer (Jan-Dec 1934)

Ten The INTERNATIONAL PHOTOGRAPHER September, 1934 "CITY OF NEW YORK". Photo by E. T. Howell. Leica Camera. Stop: f:9. Shutter: 1/60 sec. Filter: No. 2. Film: Eastman Supersensitive Panchromatic. Developer: Buffered Borax. Paper: Eastman Portrait Proofing. Gl' A COLOR 35 mm. Lenticular-Base Film: This film was first available to the European photographer, but has recently been introduced to the American miniature camera enthusiast. It does not usher in a new method of making colored photographs, the principle involved being the same as that employed by the familiar Kodacolor system of 16 mm. motion picture photography. This process is of the additive type, the film itself containing no color but a black and white record of the various hues of the subject. On projection through a suitable filter the subject appears in full color. The entire process is dependent upon a unique film whose base side has been embossed with thousands of minute cylindrical lenses. This film is loaded into the camera in the opposite fashion to normal — with its base side towards the lens. It is supplied in the usual Agfa container obviating the necessity of loading it into a magazine. About eight inches at the start are blackened as a light protection, and it is necessary before taking any picture to make three blank exposures to take up this blackened portion of the film. The second item necessary to this system is a special color filter on which the three primary colors of light are represented in bands. The Kodacolor filter contains but three bands, each of which is composed of one of the primary colors of light — red, green and blue-violet. The Agfacolor filter is divided into five or more bands, to balance the coloration, and to obtain a more even diffusion of the colors. The filter is mounted on the lens so that these bands are in a horizontal position, and this position must not be altered. In order to focus it is therefore necessary for the lens to be provided with a mount in which the front ring does not rotate when focusing. Another obvious characteristic the lens must possess is correction for chromatic aberration. MINIATURE CAMERA PHOTOGRAPHY Owners of the Leica camera can avail themselves of this color system by the acquisition of either the Hektor f:1.9, or the Summar f:2 lenses, and the necessary filter. The Summar possesses an extreme degree of correction for color. Carl Zeiss offers the Color Tessar f :2, or the Sonnar f :2, and Agfacolor filters to fit these lenses, for use with the Contax camera. The lens diaphragm remains wide open, exposure adjustment being accomplished by varying the shutter speed. If the diaphragm is closed down it will cut off the bands of the filter unevenly, interfering with the correct reproduction of the colors. A lens of the Leitz Summar type is an exception, for it is provided with an octagonal shaped diaphragm which cuts off the bands of the filter evenly. The diaphragm of this objective may be closed down when used with the Agfacolor process. The exposure required is about 15 times greater than that necessary for an ordinary orthochromatic film. As was mentioned before, the filter is mounted on the lens with the color bands in a horizontal position, this being necessary so that the bands are in the same position relatively to the minute lenses on the film. In order to simply explain the method in which this process works let us assume we are photographing an object having a single color — green. A filter allows light of its own color to pass through it, and retards the other colors, therefore light reflected from the green object passes through the green portion of the filter, but is held back by the bands of the other colors. The film as you remember is placed with the base side containing the minute lenses towards the lens, so that each minute lens on the film will form an image of the bands of the filter on the emulsion directly behind it. On development of the exposed film the minute band behind each cylindrical lens representing the green band of the filter will be dense, whereas the portions of the emulsion representing the other color bands of the filter will not contain any developed silver, since they have not been affected by light. The film is reversed, that is the developed metallic silver is dissolved away, the film exposed to light and again developed, the result being a positive. In this positive all the minute bands representing green will be clear and the rest of the film will contain dense deposits of silver. In order to view Agfacolor pictures it is necessary to project the films through a similar filter as was used in taking the pictures, with the exception that this filter is corrected for the artificial light of the projector. As the light passes through the film to the lens of the projector, each minute cylindrical lens on the film will project the image behind it so that each small band will pass through its corresponding band on the filter. In our case only the small band on the film representing green will be clear, so that light will pass only through Please mention The International Photographer when corresponding with advertisers.