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Dufaycolor

Description

Dufaycolor was a regular mosaic screen process whereby the incident light was filtered through a pattern of tiny color patches in red, green and blue, the so called réseau. When viewed from an appropriate distance, the pattern fused in the eye of the observer to form a variety of hues – similar to the dots in Pointillism paintings. The Frenchman Louis Dufay invented this pattern for still photography (see Dioptichrome) in 1908. Different companies exploited the process and changed the arrangement several times during its evolution, but the principle remained the same.

The application of the réseau onto the film was a very complicated and demanding process. The acetate film base was first coated with a blue layer (see images on this page). Then a greasy ink resist was printed in diagonal lines at an angle of 23°. The remaining lines were bleached and subsequently dyed green. Afterwards the first resist was removed and a new layer of resist lines was applied at an angle of 90° to the first two lines. The remaining lines were bleached again and subsequently dyed red. As a result of this process a pattern was formed that consisted of blue and green rectangles in combination with thinner red lines so that all patches covered areas identical in size. Finally a varnish was applied to protect the réseau and the base was coated with a panchromatic emulsion. Exposure was done through the réseau on the black-and-white emulsion and the film developed by a b/w process, a majority by a reversal process. In the different systems the order of the colors varied. For instance the Spicer-Dufay stock consisted of the red and green rectangles with blue lines.

Although the pattern was very, very fine with 19 to 25 lines per millimeter thus resulting in a million and a half patches per square inch – which equals almost 1K in resolution – it was still visible on the screen due to the high degree of magnification in projection. However, while irregular screen processes failed completely as a result of the random pattern which emerged when the film was projected, the regular screen of the Dufaycolor process was far better adapted to moving pictures. More importantly, shooting, development and screening could be operated with the usual equipment for b/w cinematography. Therefore the process was a viable and cheap alternative to Technicolor. Documentaries, experimental films and home movies were shot in Dufaycolor (see list of films on this page).

Since up to 80% of light was absorbed by the filters, all the additive screen processes required high amount of light, both for exposure and projection. To compensate for the light absorption, the Dufaycolor dyes had flat overlapping spectral transmission curves (see image on this page) which led to the desaturation of the colors. Thus the hues appear muted.

Printing from negatives posed specific problems because interferences occur when two regular patterns are overlaid on top of each other, producing an artifact called moiré. Theoretically there were two solutions to this problem. Either the negative and the print should be aligned perfectly or the pattern of the negative had to be destroyed in the printing process. Since the first solution was impossible due to the very small tolerances necessary, the second solution was applied with an aperture mask in combination with diffuse light. Similar problems arise when Dufaycolor film has to be digitized, since the diagonal pattern of the film and the orthogonal pixel structure interfere equally. Therefore scanning requires very high resolution and a light source with three narrow bands for spectral transmission in the primaries, similar to the ones used in the Dufaycolor printing process (see image on this page).

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Original Technical Papers and Primary Sources

Carson, W.H. (1934): The English Dufaycolor Film Process. In: Journal of the Society of Motion Picture Engineers, 23,1, 1934 pp. 15-26. View Quote

Dufay-Chromex (1937): The Dufaycolor Book. London: Dufay-Chromex.

Dufaycolor Company, Inc. (1938): The Dufaycolor Manual. Of Interest to Advanced Amateurs, Professional Photographers and Printers. New York: Dufaycolor, Inc.

Secondary Sources

Coe, Brian (1981): The History of Movie Photography. Westfield, N.J.: Eastview Editions, pp. 124-126. View Quote

Coote, Jack H. (1993): The Illustrated History of Colour Photography. Surbiton, Surrey: Fountain Press, pp. 47-53. View Quote

Anne Fleming (2002): A Colour Box (Len Lye Recovered). In Roger Smither (ed.): This Film is Dangerous: A Celebration of Nitrate Film. Brussels: FIAF, pp. 123-125. View Quote

Kassel Siambani, Elena von (2009): Colour in the British Documentary Film Movement. From Colour Box (1935) to Western Approaches (1944). In: Raphaëlle Costa de Beauregard (ed.): Cinéma et couleur. Paris: M. Houdiard, pp. 219-224, on pp. 220-222. View Quote

Klein, Adrian Bernhard (Cornwell-Clyne) (1940): Colour Cinematography. Boston: American Photographic Pub. Co., pp. 163-165 View Quote, 165-171 View Quote and 189-191. View Quote

Limbacher (1969): Four Aspects of the Film. A History of the Development of Color, Sound, 3-D and Widescreen Films and Their Contribution to the Art of the Motion Picture. New York: Brussel & Brussel 1969, 386 pp. 44-45. View Quote

Friedman, Joseph Solomon (1945): History of Color Photography. Boston: The American Photographic Publishing Company, pp. 166-172. View Quote

Evans, Ralph Merrill / Hanson, W.T., Jr. / Brewer, W. Lyle (1953): Principles of Color Photography. New York: Wiley, pp. 303-304. View Quote

Heymer, Gerd (1943): Die neuere Entwicklung der Farbphotographie. In: Ergänzungswerk zum Handbuch der wissenschaftlichen und angewandten Photographie. Wien: Julius Springer 1943, pp. 337-463, on pp. 387-390 [in German]. View Quote

Schultze, Werner (1953): Farbenphotographie und Farbenfilm. Wissenschaftliche Grundlagen und technische Gestaltung. Berlin/Göttingen /Heidelberg: Springer, pp. 33-36. (in German) View Quote

Brown, Simon (2012): Technical Appendix: Dufaycolor. In: Street, Sarah: Colour Films in Britain. The Negotiation of Innovation 1900-55. Basingstoke, Hampshire: Palgrave Macmillan, pp. 269-271. View Quote

Schmidt, Richard / Kochs, Adolf (1943): Farbfilmtechnik. Eine Einführung für Filmschaffende. Berlin: Hesse, pp. 54-72. (Schriftenreihe der Reichsfilmkammer, 10.) (in German) View Quote

Restoration

Anne Fleming (2002): A Colour Box (Len Lye Recovered). In Roger Smither (ed.): This Film is Dangerous: A Celebration of Nitrate Film. Brussels: FIAF, 2002, pp. 123-125. View Quote

Selected analyses

Kassel Siambani, Elena von (2009): Colour in the British Documentary Film Movement. From Colour Box (1935) to Western Approaches (1944). In: Raphaëlle Costa de Beauregard (ed.): Cinéma et couleur. Paris: M. Houdiard, pp. 219-224, on pp. 220-222. View Quote