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RA-4 is Kodak'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 is carefully exposed to form a latent image 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, [1] 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, 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 developer; 2. Bleach/fixer bath; 3. Stabilizer bath which both stabilizes the paper and washes out the chemicals; 4. 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 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, or chromogenic print.
Photographic processing or photographic development is the chemical means by which photographic film or paper is treated after photographic exposure to produce a negative or positive image. Photographic processing transforms the latent image into a visible image, makes this permanent and renders it insensitive to light.
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 visible image; with most papers the image density from exposure can be sufficient to not require further development, aside from fixing and clearing, though latent exposure is also usually present. The light-sensitive layer of the paper is called the emulsion. The most common chemistry was based on silver halide but other alternatives have also been used.
In photography, reversal film or slide film is a type of photographic film that produces a positive image on a transparent base. Instead of negatives and prints, reversal film is processed to produce transparencies or diapositives. Reversal film is produced in various sizes, from 35 mm to roll film to 8×10 inch sheet film.
The E-6 process is a chromogenic photographic process for developing Ektachrome, Fujichrome and other color reversal photographic film.
The gelatin silver process is the most commonly used chemical process in black-and-white photography, and is the fundamental chemical process for modern analog color photography. As such, films and printing papers available for analog photography rarely rely on any other chemical process to record an image. A suspension of silver salts in gelatin is coated onto a support such as glass, flexible plastic or film, baryta paper, or resin-coated paper. These light-sensitive materials are stable under normal keeping conditions and are able to be exposed and processed even many years after their manufacture. The "dry plate" gelatin process was an improvement on the collodion wet-plate process dominant from the 1850s–1880s, which had to be exposed and developed immediately after coating.
Photographic printing is the process of producing a final image on paper for viewing, using chemically sensitized paper. The paper is exposed to a photographic negative, a positive transparency , or a digital image file projected using an enlarger or digital exposure unit such as a LightJet or Minilab printer. Alternatively, the negative or transparency may be placed atop the paper and directly exposed, creating a contact print. Digital photographs are commonly printed on plain paper, for example by a color printer, but this is not considered "photographic printing".
C-41 is a chromogenic color print film developing process introduced by Kodak in 1972, superseding the C-22 process. C-41, also known as CN-16 by Fuji, CNK-4 by Konica, and AP-70 by AGFA, is the most popular film process in use, with most, if not all photofinishing labs devoting at least one machine to this development process.
Instant film is a type of photographic film that was introduced by Polaroid Corporation to produce a visible image within minutes or seconds of the photograph's exposure. The film contains the chemicals needed for developing and fixing the photograph, and the camera exposes and initiates the developing process after a photo has been taken.
The science of photography is the use of chemistry and physics in all aspects of photography. This applies to the camera, its lenses, physical operation of the camera, electronic camera internals, and the process of developing film in order to take and develop pictures properly.
A minilab is a small photographic developing and printing system or machine, as opposed to large centralized photo developing labs. Many retail stores use film or digital minilabs to provide on-site photo finishing services.
Print permanence refers to the longevity of printed material, especially photographs, and preservation issues. Over time, the optical density, color balance, lustre, and other qualities of a print will degrade. The rate at which deterioration occurs depends primarily on two main factors: the print itself, that is, the colorants used to form the image and the medium on which image resides, and the type of environment the print is exposed to.
The ADOX brand for photographic purposes has been used by three different companies since its original conception over one hundred fifty years ago. ADOX was originally a brand name used by the German company, Fotowerke Dr. C. Schleussner GmbH of Frankfurt am Main, the world's first photographic materials manufacturer. In 1962 the Schleussner family sold its photographic holdings to DuPont, an American company. DuPont used the brand for its subsidiary, Sterling Diagnostic Imaging for X-ray films. In 1999, Sterling was bought by the German company Agfa. Agfa did not use the brand and allowed its registration to lapse in 2003. Fotoimpex of Berlin, Germany, a company founded in 1992 to import photographic films and papers from former eastern Europe immediately registered the brand and today ADOX is a brand of black and white films, photographic papers and photochemistry produced by ADOX Fotowerke GmbH based in Bad Saarow near Berlin.
LightJet is a brand of hardware used for photographic printing of digital images to photographic paper and film. LightJet printers are no longer manufactured but are however remanufactured and resold; and their lasers are still manufactured.parts and service still available.
The conservation and restoration of photographs is the study of the physical care and treatment of photographic materials. It covers both efforts undertaken by photograph conservators, librarians, archivists, and museum curators who manage photograph collections at a variety of cultural heritage institutions, as well as steps taken to preserve collections of personal and family photographs. It is an umbrella term that includes both preventative preservation activities such as environmental control and conservation techniques that involve treating individual items. Both preservation and conservation require an in-depth understanding of how photographs are made, and the causes and prevention of deterioration. Conservator-restorers use this knowledge to treat photographic materials, stabilizing them from further deterioration, and sometimes restoring them for aesthetic purposes.
Harman Technology Limited, trading as Ilford Photo, is a UK-based manufacturer of photographic materials known worldwide for its Ilford branded black-and-white film, papers and chemicals and other analog photography supplies. Historically it also published the Ilford Manual of Photography, a comprehensive manual of everything photographic, including the optics, physics and chemistry of photography, along with recipes for many developers.
Chromogenic photography is photography that works by a chromogen forming a conventional silver image and then replacing it with a dye image. Most films and papers used for color photography today are chromogenic, using three layers, each providing their own subtractive color. Some chromogenic films provide black-and-white negatives, and are processed in standard color developers. In this case, the dyes are a neutral color.
A chromogenic print, also known as a C-print or C-type print, a silver halide print, or a dye coupler print, is a photographic print made from a color negative, transparency or digital image, and developed using a chromogenic process. They are composed of three layers of gelatin, each containing an emulsion of silver halide, which is used as a light-sensitive material, and a different dye coupler of subtractive color which together, when developed, form a full-color image.
Analog photography, also known as film photography, is a term usually applied to photography that uses chemical processes to capture an image, typically on paper, film or a hard plate. These processes were the only methods available to photographers for more than a century prior to the invention of digital photography, which uses electronic sensors to record images to digital media. Analog electronic photography was sometimes used in the late 20th century but soon died out.