Chromogenic photography is

photography Photography is the visual arts, art, application, and practice of creating images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is empl ...

that works by a

chromogen In chemistry, the term chromogen refers to a colourless (or faintly coloured) chemical compound that can be converted by chemical reaction into a compound which can be described as "coloured" (a chromophore). There is no universally agreed definiti ...

forming a conventional silver image and then replacing it with a

dye Juan de Guillebon, better known by his stage name DyE, is a French musician. He is known for the music video of the single "Fantasy Fantasy is a genre of speculative fiction that involves supernatural or Magic (supernatural), magical ele ...

image. Most films and papers used for color photography today are chromogenic, using three layers, each providing their own

subtractive color Subtractive color or subtractive color mixing predicts the spectral power distribution of light after it passes through successive layers of partially absorbing media. This idealized model is the essential principle of how dyes and pigments are ...

. Some chromogenic films provide black-and-white negatives, and are processed in standard color developers (such as the C-41 process). In this case, the dyes are a neutral color.

Description

Chromogenic

film A film, also known as a movie or motion picture, is a work of visual art that simulates experiences and otherwise communicates ideas, stories, perceptions, emotions, or atmosphere through the use of moving images that are generally, sinc ...

paper Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, Textile, rags, poaceae, grasses, Feces#Other uses, herbivore dung, or other vegetable sources in water. Once the water is dra ...

contains one or many layers of

silver halide A silver halide (or silver salt) is one of the chemical compounds that can form between the Chemical element, element silver (Ag) and one of the halogens. In particular, bromine (Br), chlorine (Cl), iodine (I) and fluorine (F) may each combine wit ...

(AgX) emulsion, along with

dye couplers Dye coupler is present in chromogenic film and paper used in photography, primarily color photography. When a color developer reduces ionized (exposed) silver halide crystals, the developer is oxidized, and the oxidized molecules react with dye ...

that, in combination with processing chemistry, form visible

dyes Juan de Guillebon, better known by his stage name DyE, is a French musician. He is known for the music video of the single "Fantasy (DyE song), Fantasy" from his first album ''Taki 183 (album), Taki 183''. This video became popular, attracting ...

. In processing, the silver image of each layer is first developed. In concert with the dye couplers in each layer, the process subsequently forms dyes only in those areas where silver is present. In full-color chromogenic materials, multiple layers of emulsion are sensitized to different wavelengths of

light Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400– ...

. Three layers are usually present, generally sensitive to red, green, and blue colored light. Cyan-colored dye is formed on the red-sensitive layer, magenta-colored dye is formed on the green-sensitive layer, and yellow-colored dye is formed on the blue-sensitive layer, following generally the CMY color model. Some chromogenic

black-and-white Black-and-white (B&W or B/W) images combine black and white to produce a range of achromatic brightnesses of grey. It is also known as greyscale in technical settings. Media The history of various visual media began with black and white, ...

negative films also exist, mainly to exploit the wide availability of C-41 processing. These films have softer grain and less contrast than traditional

films. In these films, a single emulsion layer has

panchromatic A panchromatic emulsion is a type of photographic emulsion that is sensitive to all wavelengths of visible light, and produces a monochrome photograph—typically black and white. Most modern commercially available film is panchromatic, and the t ...

sensitivity. The dye image is typically slightly blue because of the choice of

. Examples of black-and-white chromogenic negative films are Ilford XP2 Super and Fujifilm Neopan 400CN, produced in partnership with Ilford. Kodak have ceased production of their

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 film photography. The company is headquartered in Rochester, New York, and is incorporated i ...

BW400CN film. It is also possible to develop a standard black and white silver gelatine film or print using specially formulated chromogenic developers so that a colored dye image only remains after processing, the silver image being totally or partially bleached away during processing.The Master Photographer's Toning Book, Tim Rudman, Argentum, 2002, p146 et seq (Chromogenic Toners) Each microscopic point of chromogenic dye formation is called a dye cloud. After the formation of dyes is complete, the silver image is removed in processing by a specialty

photographic fixer Photographic fixer is a mixture of chemicals used in the final step in the photographic processing of film or paper. The fixer stabilises the image, removing the unexposed silver halide remaining on the photographic film or photographic paper, le ...

called bleach fix or blix. A processing variation called skip bleach, most popular in motion picture negative processing, leaves the silver image partially or completely intact, yielding a type of contrast enhancement. The most common chromogenic processes are C-41 for color (and chromogenic

) negative film, RA-4 for color negative paper (see Type C print), and E-6 for slide film. A great deal of research effort has been placed by manufacturers, most notably

Fujifilm , trading as , or simply Fuji, is a Japanese Multinational corporation, multinational Conglomerate (company), conglomerate headquartered in Tokyo, Japan, operating in the areas of photography, optics, Office supplies, office and Biomedical engine ...

, Ilford Photo, and

, into controlling the color and tonal characteristics of their chromogenic film and paper. The sensitization of the

emulsions, the composition and mixture of the

, and the chemical interactions of layers upon one another during processing (called interlayer effects), are the subjects of numerous patents.

is apparently unique in its use of a fourth (cyan-sensitive) color layer in certain of its negative films. Like the traditional

process, the main hazardous waste product of chromogenic processing consists of silver compounds dissolved in the used fixer. This waste is usually processed to recover the valuable dissolved

silver Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. ...

in metallic form, and to allow safe disposal of the remaining substance. A history of improper handling of waste fixer has led to environmental contamination. For example, the disposal of untreated waste fixer into the

sanitary sewer A sanitary sewer is an underground pipe or tunnel system for transporting sewage from houses and commercial buildings (but not stormwater) to a sewage treatment plant or disposal. Sanitary sewers are a type of gravity sewer and are part of ...

s and

storm drain A storm drain, storm sewer (United Kingdom, U.S. and Canada), highway drain, surface water drain/sewer (United Kingdom), or stormwater drain (Australia and New Zealand) is infrastructure designed to drain excess rain and ground water from i ...

s of

New York City New York, often called New York City (NYC), is the most populous city in the United States, located at the southern tip of New York State on one of the world's largest natural harbors. The city comprises five boroughs, each coextensive w ...

has led to high levels of dissolved silver in the

Hudson River The Hudson River, historically the North River, is a river that flows from north to south largely through eastern New York (state), New York state. It originates in the Adirondack Mountains at Henderson Lake (New York), Henderson Lake in the ...

References

* *{{cite web , url = http://notesonphotographs.eastmanhouse.org/index.php?title=Chromogenic_Print , title = Definition of Chromogenic Print on George Eastman House Notes on Photographs website , publisher = notesonphotographs.eastmanhouse.org , accessdate = 2009-10-31 , archive-url = https://web.archive.org/web/20101106224729/http://notesonphotographs.eastmanhouse.org/index.php?title=Chromogenic_Print , archive-date = 2010-11-06 , url-status = dead Photographic processes