Chromogenic color print
From Wikipedia, the free encyclopedia
Chromogenic color prints were the classic form of color photography in the latter half of the twentieth century. The first commercially available chromogenic print process was Kodacolor, introduced by Kodak in January of 1942. It is still available today, with products such as Kodak Ektacolor and Fuji Crystal Archive.
A few words about terminology: Kodak introduced a chromogenic paper with the name Type-C in the 1950s, and then discontinued the name several years later. The name Type-C and C-print have remained in popular use since this time. The chemistry used to develop chromogenic prints today is known as RA-4.
The class of color photographic processes known as chromogenic are characterized by a reaction between two chemicals to form (or give birth to) the color dyes that make up a photographic image. Chromogenic color images are composed of three main dye layers—cyan, magenta, and yellow—that together form a full color image. The light sensitive material in each layer is a silver halide emulsion—just like black and white papers. After exposure, the silver image is developed (or reduced) by a special color developer. In this reaction, the color developer in the areas of exposed silver are oxidized, and then react with another chemical, the dye coupler, which is present throughout the emulsion. This is the chromogenic reaction—the union of the oxidized developer and the dye coupler form a color dye. Different dye couplers are used in each layer, so this same reaction forms a different colored dye in each layer. A series of processing steps follow, which remove the remaining silver and silver compounds, leaving a color image composed of dyes in three layers.[1]
The exposure of a chromogenic print may be accomplished with a traditional photographic enlarger using color filters to adjust the color balance of the print. Prints can also be exposed using digital exposure systems such as the Durst Lambda, Océ LightJet and ZBE Chromira, yielding a digital C print (sometimes called a Lambda print or LightJet print). These digital systems expose the paper using red, green, and blue lasers or light emitting diodes, and have the capability of correcting paper sensitivity errors.
