:
"Color film" redirects here. For the motion picture equivalent, see Color motion picture film.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.
History
- 1942: Kodacolor (color negative process for still photography and later motion pictures)
- 1960s: Cibachrome, now officially known as Ilfochrome.
Basic color systems
Additive
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.
Subtractive
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, for printing from "separation negatives".
Kodachrome was the first commercially-available film of this type.
Modern color film
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 Neue") 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.
Main types of color film in current use
- Color negative film forms a negative (color-reversed) image when exposed, which is permanently fixed during developing. This is then exposed onto photographic paper to form a positive image.
- Color reversal film, also known as slide film, forms a negative image when exposed, which is reversed to a positive image during developing. The film can then be projected onto a screen.
Preservation issues
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.
Factors
Numerous factors can deteriorate and even destroy photographs. Some examples include:
- Residual processing chemicals
- Base and emulsion deterioration
- Improper storage and enclosures
Three signs of age that affect color photography are:
- Dark fading occurs regardless of the procedures taken to preserve a photograph and is unavoidable. It is instigated by temperature and RH. Cyan dyes will typically fade more quickly, which will make the image appear too red in color.
- Light fading occurs when materials are exposed to light, e.g. while on display. The intensity of the light source and ultraviolet (UV) rays will affect the rate of change and fade. Magenta dyes will typically fade the quickest.
- Highlight staining occurs with older color photographic papers, and is a yellowing of the border and highlight areas of a photograph.
Storage
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 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.
Recommended storage
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.
- Paper enclosures should be non-acidic, lignin-free paper and may come in either buffered or non-buffered stock. An advantage of paper is that it is generally less costly than plastic enclosures. The opaque quality of paper protects photographs from light exposure, and the porous quality protects photographs from humidity and gaseous pollutants. However, for images to be viewed, they must be removed from the enclosure, putting the materials at risk for mishandling and/or vandalism.
- Archival quality plastic enclosures are made of uncoated polyester, polypropylene, or polyethylene. The transparent quality of plastic lends itself to easier access to the image because there is no extra step to remove the photograph. Plastic is also less resistant to tears in comparison to paper. Some disadvantages include being prone to static electricity and a risk of ferrotyping (the act of moisture becoming trapped between the enclosure and item, causing the materials to stick to one another).
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.
Patents
See also
People
- Hugo Jaeger – German photographer during the Second World War in occupied Poland.
Other topics
