Chromogenic Print

In photography, a chromogenic print, also called a C-print, C-type print, or dye coupler print, is a color print made on paper with three silver halide emulsion layers sensitized to red, green, and blue light, in which the image dyes form during development. Developer oxidized by the exposed silver reacts with colorless dye couplers to produce cyan, magenta, and yellow dyes, the color-forming reaction that gives the process its name. Rudolf Fischer described this "color development" in a 1912 patent, but Agfa and Kodak made it practical only in the 1930s by anchoring the couplers within their layers. Kodak's Kodacolor introduced mass-produced negative-to-positive color prints in 1942, and its Type C paper of 1955 supplied the abbreviation C-print. By 1960 color had overtaken black-and-white in American amateur photofinishing.

Prints are usually made by projecting a color negative onto the paper in an enlarger. Processing bleaches and fixes away the silver, leaving superimposed layers of microscopic dye clouds. Prints made from transparencies on reversal paper are often called Type R. Kodak replaced fiber-based supports with resin-coated paper in 1968. Digital exposure units such as the Durst Lambda expose the same light-sensitive papers from digital files, so a digital C-print is still a chromogenic print. Stephen Shore made contact prints from 8x10 view-camera negatives for Uncommon Places, and Andreas Gursky has shown chromogenic prints at mural scale, face-mounted to acrylic.

The central critical issue is permanence. The dyes fade in light and in darkness, and leftover couplers yellow the highlights, so early Kodacolor prints from 1942 to 1954 typically survive faded to brown under a yellow stain. When color photography entered museums in the 1970s, William Eggleston printed in dye transfer, valued for its saturation and stability, while Shore worked on chromogenic paper. Silver dye bleach prints such as Cibachrome look similar but begin with preformed dyes that processing destroys where they are not needed. A Gelatin Silver Print keeps the metallic silver image that the chromogenic process removes. In this entry, Chromogenic Print refers to prints whose dye image forms in light-sensitive emulsion layers, although "C-print" is sometimes applied loosely to other color photographic prints.