Kodachrome reversal


“In the early 1920s two young Harvard graduates were experimenting with the preparation of colour plates. Both were accomplished professional musicians: Leopold Mannes, a pianist, and Leo Godowsky, Jr., a violinist. One of their early processes, patented in 1924, was for a two-colour method using a plate coated with two emulsion layers. The upper one was a slow emulsion, sensitised to blue and green light, while the bottom layer was a faster red-sensitive emulsion. The top layer was dyed yellow to prevent blue light from reaching the bottom layer. The speeds of the two layers were adjusted so that both were correctly exposed by a single exposure. They suggested several ways of developing a colour image, the most significant of which involved the use of a developer which would act on the upper layer only, not penetrating to the bottom layer before development was complete in the layer above. This allowed the silver image in the upper layer to be bleached and toned blue-green, and then the bottom layer could be developed and dye-toned orange-red. Alternatively, both layers could be developed together, and the images bleached, and a controlled penetration toning solution applied so as to tone only the upper layer, the bottom layer being subsequently dye-toned as before. Although as it stood this process was not very practical, it was to evolve into an important commercial process.

In 1922 Mannes and Godowsky had been introduced to Dr C. E. Kenneth Mees, the English Director of Research for the Eastman Kodak Company in Rochester, NY. Through his good offices, the Kodak Research Laboratory coated many experimental plates for the two amateur researchers. They discovered that a major problem with multilayer emulsions was that the dyes used to sensitise them for various colours would wander through the layers, making the red-sensitive layer slightly green-sensitive, and vice versa. In 1928 the Kodak Research Laboratory discovered a new range of sensitising dyes, some of them much less mobile than their predecessors. In 1930 Mannes and Godowsky were invited to join the staff of the Kodak Research Laboratory, where they concentrated on methods of processing multilayer films, while their colleagues worked out ways of manufacturing them. The result was the new Kodachrome film, launched in 1935. Three very thin emulsion layers were coated on film base, the emulsions being sensitised with non-wandering dyes to red, green and blue light, the red-sensitive layer being at the bottom. To deal with the unwanted blue sensitivity of the red and green layers, a yellow filter layer was provided below the top coating and above the bottom two. A single exposure produced a record of the red, green and blue content of the scene in the three layers. The exposed film was first developed to give a negative silver image in the three layers, the silver then being chemically bleached out, together with the yellow filter layer, which was a form of very finely divided silver. The film was then re-exposed to light, and all the remaining silver salts were developed in a solution containing the colourforming couplers to produce positive cyan dye images in all three layers. Next, a bleaching solution, the penetration of which could be accurately controlled, was applied to the film until the cyan dye in the top two layers was removed, but leaving that in the bottom layer intact. The bleaching solution also converted the silver image in the top two layers back into developable silver bromide. A second colour development followed, using a magenta coupler, to produce a magenta TQ8 dye image in the top two layers. Another bleaching stage removed the magenta dye from the top layer, which was then redeveloped in a yellow dyeforming developer. Now, the film had positive images in both silver and dye in each layer. The silver was removed by bleaching, leaving three clear dye images only.

The new process was released first in the form of 16 mm movie film, announced in April 1935. 8 mm movie film followed in May 1936, and 35 mm and 828 size films for still photography were released in September 1936. Because of the very complex processing involved, the Kodachrome films had to be returned to the manufacturer for processing, and the film was sold with the cost of development included. The new Kodachrome film was sensitive enough to permit exposures of 1/30 second at f/8 in good light. It sold for 12s 6d for an eighteenexposure film, including the cost of processing, which compared not unfavourably with the cost of a black and white film together with developing and printing charges. At first the films were returned in an uncut strip, for the customer to mount as slides, or to project in a film strip projector. In February 1938 a ready-mounting service was announced and the transparencies were returned to the customer in 2 x 2 inch (5 x 5 cm) card mounts. The Kodachrome film was the first commercial integral tripack film, and with its great transparency favourably contrasted with the rather dense additive screen plates and films. However, the processing cycle was very complex, and the stability of the dyes was not very good.

Both problems were resolved with the introduction of an improved process in 1938. The film, of the same construction as before, was first developed to a black and white negative. Then, the film was re-exposed through the back to a red light, which affected only the bottom layer, which was then developed in a cyan dye-forming developer. Then the film was re-exposed from the top to blue light, and the top layer was developed in a yellow dye-forming developer. Finally, a magenta dyeforming developer, containing a chemical fogging agent, was used to develop the middle layer. Now, the film had both negative and positive images in silver in each layer, and positive dye images. It remained only to bleach out the silver images, and the yellow filter layer, and a colour transparency of dye images only was left. The basis of the Kodachrome film process has remained unchanged ever since. The improved process was still complex enough that the processing of the film could only be carried out by the manufacturer, or by a laboratory equipped with the necessary complex machinery. In November 1938 the new process was made available also in sheet film form as Kodachrome Professional film, in sizes from 3 1/4 x 4 1/4 inches (8.25 x 10.8 cm) to 8 x 10 inches (20.3 x 25.4 cm). Later, the range was extended, offering sizes from 2 1/4 x 3 1/4 inches (6 x 9 cm) to 11 x 14 inches (28 x 35.5 cm). Kodachrome Professional film remained on the market until 1951, when it was superseded by Kodak Ektachrome film, introduced in 1946, which could be processed by the professional user.”

(Coe, Brian (1978): Colour Photography. The First Hundred Years 1840-1940. London: Ash & Grant, pp. 121 ff.)

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Original Technical Papers and Primary Sources

Ball, J. Arthur (1946): Quality in Color Reproduction. In: Hollywood Quarterly, 2,1, pp. 45–49, on pp. 47–48. View Quote

Mannes, L.D.; Godowsky, L. Jr. (1935): The Kodachrome Process for Amateur Cinematography in Natural Colours. In: Journal of the Society of Motion Picture Engineers, 25, July 1935, pp. 65-68. View Quote

Miller, T.H. (1949): Masking. A Technique for Improving the Quality of Color Reproduction. In: Journal of the Society of Motion Picture and Television Engineers, 52,2, 1949, pp. 133-155. View Quote

Secondary Sources

Beyer, Friedemann; Koshofer, Gert; Krüger, Michael (2010): UFA in Farbe. Technik, Politik und Starkult zwischen 1936 und 1945. München: Collection Rolf Heyne, on p. 42 View Quote, on p. 44 View Quote, on p. 46 View Quote and on p. 47. (in German) View Quote

Bordwell, David; Staiger, Janet; Thompson, Kristin (1985): The Classical Hollywood Cinema. Film Style and Mode of Production to 1960. London: Routledge, on p. 357. View Quote

Coe, Brian (1978): Colour Photography. The First Hundred Years 1840-1940. London: Ash & Grant, pp. 121 ff. View Quote

Cornwell-Clyne, Adrian (1951): Colour Cinematography. London: Chapman & Hall, pp. 427-451. View Quote

Dr. N. (1937): Mehrschichten-Film. In: Film-Kurier, 27.8.1937, Serie „Farb-Film-Fibel”. (in German) View Quote

Lavedrine, Bertrand (1998): History and Technology of Colour Photographic Processes. In: Luciano Berriatúa et al.: Tutti i colori del mondo. Il colore nei mass media tra 1900 e 1930. = All the colours of the world. Reggio Emilia: Edizioni Diabasis, pp. 117-119, on p. 118. View Quote

Meyer, Kurt (1940): Die farbenfotografischen subtraktiven Mehrschichten-Verfahren. In: Ergebnisse der angewandten physikalischen Chemie, 6,2. Leipzig: Akademische Verlagsgesellschaft, on pp. 368-370 View Quote and pp. 398-411. (In German) View Quote

Pinel, Vincent (1992): La forêt des techniques. In: Michel Ciment (ed.): Ciné mémoire. Colloque international d’information (7-9 octobre 1991). Paris: Femis, pp. 17-24, on p. 20. (in French) View Quote

Rijper, Els (2002): Kodachrome. The American Invention of Our World, 1939-1959. Delano Greenidge Editions: New York. View Quote

Ryan, Roderick T. (1977): A History of Motion Picture Color Technology. London: Focal Press, pp. 114-121. View Quote

Webers, Johannes; Westendorp, Kurt (1979): Einführung in die Kopierwerktechnik (XV). In: Fernseh- und Kinotechnik, 33,9, pp. 334–337, on p. 334. (in German) View Quote