Color photography is photography that uses media capable of representing colors which are produced chemically during the photographic processing phase. It is contrasted with black-and-white photography, which uses media capable only of showing shades of gray. It does not include hand colored or Photochrome photographs either. Some examples of color photography include prints, color negatives, transparencies and slides, and roll and sheet films.
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The colors are added as colored lights. In this system, the most common set of primary colors is red, green and blue (RGB). Maxwell's experiment was of this type, as are screen-plate methods, such as Autochrome. Modern digital photographs seen on a computer monitor are also viewed by addition of light from an RGB phosphor array.
Colors are subtracted from white light by dyes or pigments. In this system the most common set of primary colors is cyan, magenta, yellow and black (CMYK). Ducos du Hauron made several pictures by this method in the late 19th century.
Several commercial print methods were devised using the subtractive technique during the 1930s,[1] for printing from "separation negatives". Kodachrome was the first commercially-available film of this type.
The first modern ("integrated tri-pack") color film, Kodachrome, was introduced by the Eastman Kodak Company in 1935, using three colored emulsions. Most modern color films, except Kodachrome, are based on technology developed for Agfacolor (as "Agfacolor-Neu") in 1936. (In this newer technology, chromogenic dye couplers are already within the emulsion layers, rather than having to be carefully diffused in during development.) Instant color film was introduced by Polaroid in 1963.
The two types of film differ more in the processing than in the film itself. In the 1960s, the fastest color film was Kodak's High Speed Ektachrome (a reversal film), and many photographers achieved further speed increases by developing it as a negative film.
Experimentation with creating photographs that mirrored the colors of real life began as early as 1861. Each process may require different methods of preservation.
Color photographic materials are impermanent and are by nature unstable. Chromogenic color photographs, for example, are composed of yellow, magenta, and cyan organic dyes; which fade at different rates. Even when in dark storage and enclosed in the proper archival materials, deterioration is unavoidable. However, when given the proper preservation care, fading, color shifting, and discoloration can be delayed.
Numerous factors can deteriorate and even destroy photographs. Some examples include:
Three signs of age that affect color photography are:
In general, the colder the storage, the longer the "life" of color photographs. Frost-free refrigeration, more commonly known as cold storage (below freezing) is one of the most effective ways to bring a halt to developing damage to color photographic materials. Selecting this type of storage environment is costly and requires special training to remove and return items. Therefore, cool storage (above freezing) is more common and less costly, which requires that the temperature is consistently between 10–15 °C (50–59 °F) with 30–40% relative humidity with special attention to dew point to eliminate concerns for condensation. General dark storage in light tight enclosures and storage boxes is always advised for individual items. When materials are exposed to light during handling, usage, or display, light sources should be UV-filtered and intensity kept at minimum. In storage areas, 200–400 lux is recommended.
The usage of enclosures is the easiest method of preserving photographic materials from being damaged through handling and light exposure. All protective materials should pass the Photographic Activity Test (PAT) as described both by the American National Standards Institute (ANSI) in standard IT9.2-1988, and the International Organization for Standardization (ISO) in standard 18916:2007(E), Photography – Processed Photographic Materials – Photographic Activity Test for Enclosure Materials. The PAT is an archival science test that determines what kind of enclosures will preserve, prevent, and/or prolong from further deterioration while in storage.
The recommended use of archival enclosures includes each item having its own enclosure and that each enclosure is of the appropriate size. Archival enclosures may come in two different forms: paper or plastic. Choosing either option has its advantages and disadvantages.
After photographic materials are individually enclosed, housing or storage containers provide another protective barrier such as folders and boxes made from archival paperboard as addressed in ISO Standards 18916:2007 and 18902. Sometimes these containers have to be custom-made in order to properly store odd sizes. In general, flat storage of in boxes is recommended because it provides more stable support, particularly for materials that are in more fragile condition. Still, boxes and folders should never be over-filled with materials.
   | Library of Congress Prokudin-Gorskii collection - Photographer to the Tsar: Sergei Mikhailovich Prokudin-Gorskii - The Empire That Was Russia: The Prokudin-Gorskii PhotographicRecord Recreated (A Library of Congress Exhibition) |
| | Conservation Register - Care and conservation of photographs and photographic materials, Photographic conservator, Restoration of photographs, Restoring photographs, Conservation of film and negatives, Conservation of glass plates |
| | "Care and Handling and Storage of Photographs" by Mark Roosa (IFLA) - Care Handling, and Storage of Photographs: Information Leaflet |
| | Henry Wilhelm - Wilhelm Imaging Research |
| | Library of Congress - Information Leaflet: Photographs - Information Leaflet on the Care, Handling, and Storage of Photographs (Preservation, Library of Congress) |
| | National Park Service. Conserve-O-Gram (select PDF versions on menu) - About Conserve O Grams (NPS) |
| | Library of Congress List of Photographic Preservation Supplies - Supplies: Care, Handling, and Storage of Photographs (Preservation, Library of Congress) |
| | American National Standards Institute - American National Standards Institute - ANSI |
| | Cambridge in Color Photography Tutorials - Digital Photography Tutorials |
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