Dufaycolor is an earlyBritishadditive colourphotographic film process, introduced formotion picture use in 1932 and forstill photography in 1935. It was derived fromLouis Dufay [fr]'s Dioptichromeplates, a glass-based product for colour still photography, introduced in France in 1909. Both Dioptichrome and Dufaycolor worked on the same principles as theAutochrome 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 colouredstarch grains.[1] The manufacture of Dufaycolor film ended in the late 1950s.
 | This sectionneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources in this section. Unsourced material may be challenged and removed.(February 2021) (Learn how and when to remove this message) |
Thephotographic reproduction of natural colour by means of ablack-and-white photograph taken and viewed through amosaic of tiny colourfilters was an idea first patented and published byLouis Ducos du Hauron in the late 1860s, but the incomplete colour sensitivity of contemporary photographic materials made it impractical at that time.John Joly independently reinvented the concept in 1894 and attempted to commercialise it, but the first successful product based on this idea, theAutochromeplate, did not reach the market until 1907. Several competing mosaic colour screen plate products soon appeared, includingLouis Dufay [fr]'s Dioptichrome plate, but the Autochrome plate remained by far the most popular and the production of Dioptichrome was ended in 1914.[2] A film-based version of Autochrome was introduced in 1931, shortly before the first Dufaycolor product appeared.
These plate and film products differed substantially only in the means used to manufacture the colour mosaic layer and its resulting pattern and fineness. Autochrome's mosaic was a random array of dyedpotato starch grains, too small to be individually visible without a microscope. Most competing products employed a coarser geometric pattern created by one of the many methods devised and patented during that era. Dufaycolor's filter layer was of the geometric type, but its proprietary manufacturing process produced an unusually fine-patterned mosaic.
A very thin coating ofcollodion on one side of thefilm base was dyed blue, printed with closely spaced fine lines using a water-repelling greasy ink, and bleached. The clear spaces created were then dyed green. The ink was removed, and new ink lines were printed at a 90-degree angle to the blue and green lines. The new gaps were bleached and dyed red, resulting in a colourfilter mosaic, known as aréseau, consisting of alternating green and blue squares between red lines, and having roughly one million colour filter elements per square inch.[3] 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 apanchromatic black-and-whitephotographic emulsion. When exposed to light through the base and itsréseau, the bit of emulsion behind each colour element recorded only the amount of light of that primary colour striking the film at that point.[4]
Dufaycolor was normally areversal film which wasprocessed to produce the final positive image, instead of anegative, on the original film. In the case of still photographs, the result, known as adiapositive ortransparency, 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 aslide. Small-gaugehome 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.[5]
Upon projection, theréseau serves to filter the white projection light, so that the colours reaching the screen correspond to those in the recorded scene. For example, intensely red objects are represented by transparent areas behind the red filter elements and opaque areas behind the green and blue elements. The same principle operates with intensely green or blue objects. 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. Typical modernLCD video displays work similarly, combining a backlit black-and-white image layer with an array of hair-thin red, green, and blue vertical filter stripes.
Finished Dufaycolor films suffer from the two shortcomings inherent in all mosaic colour screen processes: theréseau absorbs most of the viewing or projection light, requiring the use of an unusually bright light for normal image brightness, and if too greatly magnified, the individual colour filter elements become disruptively visible.
Louis Dufay's interests were purchased by British paper manufacturing firm Spicers in 1926, which then funded research to produce a workablecolour motion picture film. In 1932, Spicers finally released Dufaycolor as a motion picture product.[6]
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, especiallyKodachrome, were not available in the sizes used by typical snapshot cameras, and amateurdarkroom enthusiasts couldprocess Dufaycolor at home almost as easily as black-and-white film. Medium and large format cut films for professional use were also made.[citation needed]
Dufaycolor was used in only two British-made feature films: the two colour sequences inRadio Parade of 1935 (1934), and the all-colourSons of the Sea (1939), directed byMaurice Elvey.[6] It was used forshort films;Len Lye, for instance, used it for his filmsKaleidoscope (1935),A Colour Box (1935), andSwinging the Lambeth Walk (1940). TheGPO Film Unit used it for short documentaries such asHow the Teleprinter Works (1940).[7] Dufaycolor was also used for the final minutes of the Italianaviation filmThe Thrill of the Skies (1939). Dufaycolor was used for theBritish Movietone News footage ofKing George V's 1935silver jubilee procession.[citation needed]Dufaycolor was used for the Polish anti-Nazi filmCalling Mr. Smith (1943) byStefan Themerson about Nazi crimes inGerman-occupied Europe and about lies of Nazi propaganda.[8][9][10]
Although less expensive than other colour films, Dufaycolor was still expensive compared to black-and-white film. As colour became more common in motion pictures, Dufaycolor was superseded by technologically superior processes, such as three-stripTechnicolor. Dufaycolor remained the only successfully implementedadditive film stock for motion pictures until 1977, whenPolaroid introducedPolavision, a system for making and viewing "instant" colour home movies that proved to be a spectacular commercial failure and was soon discontinued.[4]