Chromogenic color print
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Chromogenic color prints are full-color photographic prints made using chromogenic materials and processes. These prints may be produced from an original which is a color negative, slide, or digital image. The chromogenic print process was nearly synonymous with the 20th century color snapshot.
Traditional Chromogenic Prints
The first commercially available chromogenic print process was Kodacolor, introduced by Kodak in January 1942. Kodak introduced a chromogenic paper with the name Type-C in the 1950s, and then discontinued the name several years later. The terminology 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. As of 2010, the major lines of professional chromogenic print paper are Kodak Endura and Fujifilm Crystal Archive. Plastic chromogenic "papers" such as Kodak Duratrans and Duraclear are used for producing backlit advertising and art.
The class of color photographic processes known as chromogenic is characterized by a reaction between two chemicals to create 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 of three layers, so this same reaction forms a different colored dye in each layer. Responding to both exposure and development, a blue-light sensitive layer forms yellow dye, a green-light sensitive layer forms magenta dye, and a red-light sensitive layer forms cyan dye. A series of processing steps follow, which remove the remaining silver and silver compounds, leaving a color image composed of dyes in three layers. 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.
Positive to Positive Printing
Fujifilm, Kodak, and Agfa have historically manufactured paper and chemicals for the R-3 process, a chromogenic process for making Type R prints. As of late 2008, all of these companies have ceased to produce Type R paper, although Fujifilm still has some stocks remaining.
Another positive-to-positive process is Ilfochrome, which is sometimes also referred to as a Type R process. Ilfochrome is a dye destruction process, with materials, processing, and results quite different from the R-3 process.
Digital C-Type Printing
Prints can also be exposed using digital exposure systems such as the Durst Lambda, Océ LightJet and ZBE Chromira, yielding a digital C-Type print (sometimes called a Lambda print or LightJet print). The LightJet and the Lambda both use RGB lasers to expose light-sensitive material to produce a latent image that is then developed using conventional silver based photographic chemicals. The Chromira uses LEDs instead of lasers which results in a faster imaging time but can result in banding and Moiré patterns in fine details if photographs submitted to the printer are at a size that differs from the actual crop and pixel resolution of the image file. All of the aforementioned printers utilise ICC colour profiles to achieve colour and density accuracy and also to correct paper sensitivity errors. The same technology can also be used to produce digital silver gelatin bromide black and white prints.
- Weaver, Gawain; Long, Zach (2009), Chromogenic Characterization: A Study of Kodak Color Prints, 1942-2008, retrieved 30 October 2009