In
chemistry
Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, structure, proper ...
, orthochromasia is the property of a
dye or stain to not change color on binding to a target, as opposed to
metachromatic stains, which change color. The word is derived from the Greek ''
orthos'' (correct, upright), and chromatic (color).
Toluidine blue is an example of a partially orthochromatic dye, as it stains
nucleic acids
Nucleic acids are biopolymers, macromolecules, essential to all known forms of life. They are composed of nucleotides, which are the monomers made of three components: a 5-carbon sugar, a phosphate group and a nitrogenous base. The two main cl ...
by its orthochromatic color (blue), but stains mast cell granules in its metachromatic color (red).
In
spectral
''Spectral'' is a 2016 3D military science fiction, supernatural horror fantasy and action-adventure thriller war film directed by Nic Mathieu. Written by himself, Ian Fried, and George Nolfi from a story by Fried and Mathieu. The film stars J ...
terms, orthochromasia refers to maintaining the position of spectral peaks, while metachromasia refers to a shift in wavelength, becoming either
shorter or
longer.
In photography, an orthochromatic light spectrum is one devoid of red light.
In biology, orthochromatic refers to the greyish staining because of acidophilic and basophilic mixture in the cell.
Orthochromatic photography
Orthochromatic photography refers to a
photographic emulsion
Photographic emulsion is a light-sensitive colloid used in film-based photography. Most commonly, in silver-gelatin photography, it consists of silver halide crystals dispersed in gelatin. The emulsion is usually coated onto a substrate of glas ...
that is sensitive to only blue and green light, and thus can be processed with a red
safelight. The increased blue sensitivity causes blue objects to appear lighter, and red ones darker. A
cyan
Cyan () is the color between green and blue on the visible spectrum of light. It is evoked by light with a predominant wavelength between 490 and 520 nm, between the wavelengths of green and blue.
In the subtractive color system, or CMYK col ...
lens filter (which removes red light) can be used with standard
panchromatic film
Panchromatic emulsion is a type of black-and-white photographic emulsion that is sensitive to all wavelengths of visible light.
Description
A panchromatic emulsion renders a realistic reproduction of a scene as it appears to the human eye, alth ...
to produce a similar effect.
Orthochromatic films were first produced by
Hermann Wilhelm Vogel
Hermann Wilhelm Vogel (26 March 1834 – 17 December 1898) was a German photochemist and photographer who discovered dye sensitization, which is of great importance to photography.
Academic career
After finishing school in Frankfurt (Oder), ...
in 1873 by adding small amounts of certain
aniline
Aniline is an organic compound with the formula C6 H5 NH2. Consisting of a phenyl group attached to an amino group, aniline is the simplest aromatic amine. It is an industrially significant commodity chemical, as well as a versatile starti ...
-based dyes to photographic emulsions, which until that time had been sensitive to blue light only. This work was extended by others including
Josef Maria Eder
Josef Maria Eder (16 March 1855 – 18 October 1944) was an Austrian chemist who specialized in the chemistry of photography, and who wrote a comprehensive early history of the technical development of chemical photography.
Life and work
Eder was ...
, who introduced the use of the red dye
erythrosine in 1884.
See also
*
Panchromatic
Panchromatic emulsion is a type of black-and-white photographic emulsion that is sensitive to all wavelengths of visible light.
Description
A panchromatic emulsion renders a realistic reproduction of a scene as it appears to the human eye, altho ...
References
Photographic film types
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