RA-4 process
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RA-4 is
Kodak The Eastman Kodak Company (referred to simply as Kodak ) is an American public company that produces various products related to its historic basis in analogue photography. The company is headquartered in Rochester, New York, and is incorpor ...
's proprietary name for the chemical process most commonly used to make color photographic prints. It is used for both minilab wet silver halide digital printers of the types most common today in photo labs and drug stores, and for prints made with older-type optical enlargers and manual processing. More specifically, common color
photographic paper Photographic paper is a paper coated with a light-sensitive chemical formula, like photographic film, used for making photographic prints. When photographic paper is exposed to light, it captures a latent image that is then developed to form a ...
is carefully exposed to form a
latent image {{citations needed, date=November 2015 A latent image is an invisible image produced by the exposure to light of a photosensitive material such as photographic film. When photographic film is developed, the area that was exposed darkens and for ...
of the picture, and then the paper is run through the series of chemicals that together comprise the RA-4 process to convert the latent image into the final print. RA-4 uses Color Developing Agent 3, in combination with color couplers in the emulsion to generate color dyes. RA-4 is a standardized chromogenic process used worldwide to make prints with a variety of equipment, photographic paper, and chemicals. Kodak created the RA-4 process for its color negative photographic papers.
Fuji Fuji may refer to: Places China * Fuji, Xiangcheng City (ไป˜้›†้•‡), town in Xiangcheng City, Henan Japan * Mount Fuji, the tallest mountain in Japan * Fuji River * Fuji, Saga, town in Saga Prefecture * Fuji, Shizuoka, city in Shizuoka Prefec ...
, Agfa, and other present and past photographic supply companies also make or have made both papers that are compatible with the Kodak chemicals, and chemicals that are compatible with the Kodak papers. These other companies typically call their equivalent processes by other names, but to most photographers, RA-4 is used as a generic term. The actual chemical process occurs at 100 degrees F. The steps: 1. The paper ( glossy or matte) is taken through color
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; 2. Brief wash; 3. Bleach/fixer bath; 4. The chemicals are washed out of the paper by water; 5. Drying. Since the paper is Resin Coated, it dries flat and even. This processing can be done in a machine, e.g. in a minilab, where rotary tubes transport the film through the baths, or by the photo hobbyist in a
darkroom A darkroom is used to process photographic film, to make prints and to carry out other associated tasks. It is a room that can be made completely dark to allow the processing of the light-sensitive photographic materials, including film and ph ...
setting, using trays for each bath. Current manufacturers of RA-4 Chemistry include Kodak, Freestyle, Rollei, Unicolor and Tetenal as of 2017. The result of RA-4 processing is a Type C print.


References


External links


Process RA-4 Publication: Z-130
- Official Kodak lab manual Photographic film processes Kodak {{Photo-stub