Patent GB-245198-A (GB)
Title: Improvements in or relating to color photography
IPC: G03C7/26
Filed: 1924-10-01
Abstract: 245,198. Mannes, L. D., and Godowsky, L. Oct. 1, 1924. Colour photography; plates and films with multiple sensitive layers.-A photograph in natural colours is produced by a single exposure and a single printing operation by employing, for the production of the negative and positive images, supports each carrying on one side two or more superimposed emulsion layers sensitized respectively for the different component colours, the images formed thereon being coloured after development. The component colour images of either the negative or the positive may be developed either successively or simultaneously. For a two-colour result, a camera exposure is made on a plate or film carrying on one side two superimposed silver bromide emulsion layers, of which the lower is fast and sensitive to red or orangered, and the upper is slower and sensitive to green or green-blue. The upper layer may contain a yellow dye, and filters may be used to regulate the exposures of the layers. If successive development of the layers is adopted, the upper layer is treated with a rapid surface developer which is removed before it penetrates to the lower layer. The developed image is toned green, as with a ferric-vanadium bath, whereafter the lower layer is developed, as with diamidophenol. The film is fixed, washed, and dyemordanted with a bath that will not affect the upper image, and the lower image is dyed orangered, as with a mixture of fuchsine, auramine, and acetic acid. If simultaneous development of the two layers is adopted, as in a bath of acid diamidophenol, they are fixed, the upper image only is toned green by a short immersion in the green toning-bath, and the lower image is dye-toned as before. From the coloured negative so produced, a positive is printed on identical film material, and is developed and coloured in the same way. The positive is preferably printed through a dichroic filter. A modified process is described in which the colours in the negative are reversed, and are re-reversed in the positive printed therefrom. The two-colour process may be employed to yield three-colour results by taking advantage of the fact that, owing to the presence of yellow dye in the upper emulsion layer, the blue-violet component of the incident light is recorded mainly at the surface, while the green component is recorded throughout the depth of the layer. The three component images (negative or positive) are developed simultaneously and coloured by successive toning and dyeing operations. A trichroic filter is preferably employed in producing the negative. A three-colour process is also described in which a camera-exposure is made on a plate or film coated in succession on one side with three emulsion layers, first a very rapid redsensitive emulsion, then a rapid orthochromatic emulsion to record green, and finally a slow ordinary emulsion to record blue-violet, the top layer being preferably dyed yellow as before. The images are preferably all developed together, and the upper two are coloured blue and green in the same way as for a two-colour result. The film is resensitized with bichromate and printed through the support, so that the red-value silver image in the lower-most layer is printed in the gelatin. The unexposed parts are then dyed red, and the silver image is dissolved out of the lowermost layer. From the coloured negative so produced a positive is printed upon a film coated in succession with a panchromatic emulsion to record yellow, a slower red-sensitive emulsion, and a slow orthochromatic emulsion to record bluegreen.