Australian National Film and Sound Archive
The new gaps were bleached and dyed red, resulting in a colour filter mosaic, known as a réseau, consisting of alternating green and blue squares between red lines, and having roughly one million colour filter elements per square inch. Upon projection, the réseau serves to filter the white projection light, so that the colours reaching the screen correspond to those in the recorded scene. Less saturated tints, and non-primary colours such as orange, yellow, and purple, along with neutral grays and white, are reproduced by various proportions of red, green, and blue light blending together in the viewer's eye due to the tiny size and close spacing of the individual elements. In very early years, different arrangements of the same colours were used, the lines being green or blue instead of red and sometimes intersecting the other colours diagonally. After a final ink removal and the application of an isolating varnish, the same side of the film base was coated with a panchromatic black-and-white photographic emulsion.
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A very thin coating of collodion on one side of the film base was dyed blue, printed with closely spaced fine lines using a water-repelling greasy ink, and bleached. J. Chambers, Dir., How the Teleprinter Works, GPO Film Unit, 1940; YouTube. Dufaycolor remained the only successfully implemented additive film stock for motion pictures until 1977, when Polaroid introduced Polavision, a system for making and viewing "instant" colour home movies that proved to be a spectacular commercial failure and was soon discontinued. Roll films for colour snapshots followed in 1935 and remained popular with some amateurs until manufacture ceased in the late 1950s. They were cheaper than the more sophisticated film types, some of which, especially Kodachrome, were not available in the sizes used by typical snapshot cameras, and amateur darkroom enthusiasts could process Dufaycolor at home almost as easily as black-and-white film. Small-gauge home movie films were also unique original positives, but to facilitate use for theatrical motion pictures, which required the production of numerous identical positive prints, a two-step negative-positive 35 mm version was introduced. As colour became more common in motion pictures, Dufaycolor was superseded by technologically superior processes, such as three-strip Technicolor. Although less expensive than other colour films, Dufaycolor was still expensive compared to black-and-white film.
In the case of still photographs, the result, known as a diapositive or transparency, was usually viewed directly by means of a backlight, but it could also be bound up between cover glasses or mounted in a small frame for use in a projector, in which form it was commonly called a slide. Autochrome's mosaic was a random array of dyed potato starch grains, too small to be individually visible without a microscope. Both Dioptichrome and Dufaycolor worked on the same principles as the Autochrome process, but achieved their results using a layer of tiny colour filter elements arrayed in a regular geometric pattern, unlike Autochrome's random array of coloured starch grains. The same principle operates with intensely green or blue objects. For example, intensely red objects are represented by transparent areas behind the red filter elements and opaque areas behind the green and blue elements. When exposed to light through the base and its réseau, the bit of emulsion behind each colour element recorded only the amount of light of that primary colour striking the film at that point. These plate and film products differed substantially only in the means used to manufacture the colour mosaic layer and its resulting pattern and fineness. This was creat ed with the help of GSA Con te nt Generator D emoversion.
Most competing products employed a coarser geometric pattern created by one of the many methods devised and patented during that era. John Joly independently reinvented the concept in 1894 and attempted to commercialise it, but the first successful product based on this idea, the Autochrome plate, did not reach the market until 1907. Several competing mosaic colour screen plate products soon appeared, including Louis Dufay's Dioptichrome plate, but the Autochrome plate remained by far the most popular. Louis Dufay's interests were purchased by British paper manufacturing firm Spicers in 1926, which then funded research to produce a workable colour motion picture film. Dufaycolor - The Spectacle of Reality and British National Cinema, a recent article on the process and the history of its use. AHRB Centre for British Film and Television Studies. Dufaycolor was also used for the final minutes of the Italian aviation film The Thrill of the Skies (1939). Dufaycolor was used for the British Movietone News footage of King George V's 1935 silver jubilee procession. Dufaycolor on Timeline of Historical Film Colors, a comprehensive bibliography, many photographs of historical Dufaycolor films, patents, and links. Pritchard, Brian. (n.d.) Some information about the 35 mm negative-positive version and a summary Dufaycolor chronology.
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