Understanding colors of Dufaycolor
Jan Hubička
Dufaycolor was an additive process of color photography introduced in 1932 for motion film and in 1935 for still photography (the same year as Kodachrome). It was the most advanced color screen process, but is under-appreciated today because the dyes in their emulsion tend to fade. In a previous talk I discussed the possibility of digital color reconstruction based on high resolution scans of original transparencies (ideally including an infrared channel) which makes it possible to reproduce the original colors.
In order to make the color reconstruction historically authentic, it is necessary to understand details of the process. I will discuss the historical method of printing the Dufaycolor color screen (reseau) and the properties of dyes used to produce it. Since published data are incomplete, imprecise, and often contradicting each other, I implemented a full digital simulator of the process which makes it possible to turn the spectrum of light seen by the camera into the expected response of Dufaycolor film. I discuss lessons learned from the experiment and how that improves our understanding of the accuracy of color recordings.
There are three main goals of our project:
1) We would like to find practical methods of digitizing early color photographs which faithfully and completely reproduce the physical object as it is today.
2) We would like to digitally restore the colors to their appearance at the time of original processing.
3) We would like to adapt modern algorithms for processing RAW camera images to digitally restore the color of the scene to how it would have appeared at the time of capture and based on that understand the color vision of Dufaycolor film.
This is joint work with Linda Kimrova (Charles University) and Doug Peterson (DT Heritage) with significant support from the National Geographic Society.
Jan Hubička is following on from his presentation to the group on Tuesday, December 19, 2023 when he spoke on Digitizing Paget, Finlay and Dufaycolor photographs at National Geographic Society. He is an associate professor at the Department of Applied Mathematics, software developer at SUSE LINUX s.r.o. and also a co-founder and a co-director of Šechtl and Voseček Museum of Photography in Tábor, Czech Republic. His interest in early color photography was sparked by Autochromes taken by his great grandfather, Josef Jindřich Šechtl. In 2006 he organized exhibition of early color photographs by Sergei Mikhailovich Prokudin-Gorsky (first in Europe except for Moscow) for which he made his own tool composing scans of the separation negatives. In 2007 he organized exhibition of (reproductions of) Czech Autochromes which got him into contact with American collector of early color photography, Mark Jacobs. He helped to digitize important part of Mark Jacobs' collection and in 2012 organized exhibition “When the World Turned to Color Early Color Photography from the Mark Jacobs Collection”. Work on regular color screen processes started in 2011 for exhibition of photographs from the American Colony Collection where Mark Jacobs identified negatives for Finlay color process. He also co-organized two international workshops on early color photography, "Legacy of three-color photography" in 2008 and "Space, Color, Motion" in 2013.
Cornwell-Clyne, Adrian. Colour Cinematography. United Kingdom: Champman & Hall, 1951.
https://archive.org/details/in.gov.ignca.15062/page/n303/mode/2up
Thorne Baker, Thomas. The Spicer-Dufay Colour Film Process. The Photographic Journal, March, 1932, 109-117
https://archive.rps.org/archive/volume-72
Bonamico, C., and T. Thorne Baker. "Dyes and Colours in Photography." Journal of the Society of Dyers and Colourists 49, no. 4 (1933): 103-105.
https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1478-4408.1933.tb01749.x
The Dufaycolor Manual: Of Interest to Advanced Amateurs, Professional Photographers and Printers. United States: Dufaycolor, Incorporated, 1938.
https://filmcolors.org/wp-content/uploads/2013/05/Dufaycolor_Manual_1938_print.pdf
Harrison and Horner. "The Principles of Dufaycolor prinitng" The photographic journal, May 1939, 320-329
https://archive.rps.org/archive/volume-79
Renwick, F. F.. "The Dufaycolour Process" The photographic journal, January 1935, 28-37
https://archive.rps.org/archive/volume-75/734248
Developing a RAW photo "by hand"
https://www.odelama.com/photo/Developing-a-RAW-Photo-by-hand/