Subtractive 3 color: Stripping film
( E. I. DuPont Company)
Ryan, Roderick T. (1977): A History of Motion Picture Color Technology. London: Focal Press, pp. 134-135
” DuPont Stripping Negative
S. T. Tripac, a black and white stripping film that produced three separation negatives, was introduced by the E. I. DuPont Company in 1949.35 Exposure was made using a conventional motion picture camera whose gate had been adjusted to accommodate the extra thickness of the film.
S. T. Tripac had a film speed of A.S.A. 12 when exposed to a tungsten light source having a color temperature of 3200°K. The film speed to daylight was A.S.A. 8 when exposed through a Wratten 85B filter.
The structure of the film was similar to the combination of a bipack and a single film cemented together (Fig. 46). The three light sensitive emulsions were in the center between two film bases. When loaded in the camera the side of the film toward the lens was the bipack with its support facing the lens and the blue and green sensitive layer following it. This was connected to the third or red sensitive layer and its support by a red filter layer. After exposure the film was developed in a conventional black and white developer and fixed in a hardening fixer. Then the film was immediately immersed in a fresh stop bath and the front bipack film was stripped from the rear film and its support.
The excess solution was removed and the bipack was immersed in the transfer solution for two minutes. It was then rolled in contact with a gelatin coated support and left to set for two minutes. The two layers could then be separated by pulling off at an angle, the green record being transferred to the new support (Fig. 47). The three separate films were then washed and dried and were ready for printing by one of several methods that employ three separation negatives as the original.36
35 Sease, V. B., “DuPont’s New Color Film,” American Cinematographer, 1949, pp. 240, 257-258.
36 Spiller, Gino, “Modern Techniques of Color Film Processing” (unpublished Master’s thesis, University of Southern California, 1952).”
(Ryan, Roderick T. (1977): A History of Motion Picture Color Technology. London: Focal Press, pp. 134-135.)
Timeline of Historical Film Colors by Barbara Flueckiger is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.