An obsolete additive colour film process, in which the film was coated with a very large number of minute red, blue and green filters, the proportion of the three colours being such that the resulting colour was a neutral grey when the film was viewed at a distance. Made by Dufay-Chromex Ltd. London&The Dufaycolor Company Inc., New York.The filters were printed directly on to the base and covered with emulsion, thus overcoming the registration problems of many other additive processes. Dufay color 35 mm film has 20 lines to the millimetre. From experience the screen or reseau is becomes invisible at some 60 feet from a 25 foot screen.
Film was threaded in the camera with its base and filter grid towards the light, so that the light reflected from each point in the scene was filtered according to its blueness, greenness and redness before it reached the emulsion . Thus the image was formed in silver opacities corresponding to the original colours, and it was only necessary to reverse these into transmittances by reversal processing to recreate the original colours when the film was viewed by transmitted light.
When the film was projected, the transmission of each minute group of three-coloured filters through the emulsion over it corresponded to the brightness of the original scene. However, the mesh of the reseau, the light loss in the screen, and the dilution of colour resulting from overlapping filter transmissions tended to make the system inefficient in spite of its many attractions, and it was abandoned. 1
Although many additive processes were developed for still photography (Autochrome, Agfacolor, Omnicolor, and Paget and Finby for example) Dufaycolor was the only successful motion picture film process until the development of a Polaroid®process in the 1970s.
Other obsolete colour processes that were recorded in November 1930 of the SMPE Journal include: Multicolor, Sennett Color, Harriscolor, Fox Color, and Vitacolor. Some were additive systems or the genisus of the later subtractive colour systems.
Subtractive processes, in general, have three principal advantages. First, the colour is in the prints when they leave the laboratory, doing away with the possibility of error in the projection booths; second, special projection equipment is not needed; and third, less light is necessary to project the subtractive prints.
1 1969, The Focal Encyclopedia of Film and Television Techniques, Focal Press, London, New York