In
chemistry
Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...
, orthochromasia is the property of a
dye or stain to not change color on binding to a target, as opposed to
metachromatic Metachromasia (var. metachromasy) is a characteristical change in the color of staining carried out in biological tissues, exhibited by certain dyes when they bind to particular substances present in these tissues, called chromotropes. For example ...
stains, which change color. The word is derived from the Greek ''
orthos'' (correct, upright), and chromatic (color).
Toluidine blue
Toluidine blue, also known as TBO or tolonium chloride (International Nonproprietary Name, INN) is a blue cationic (basic) dye used in histology (as the toluidine blue stain) and sometimes clinically.
Test for lignin
Toluidine blue Solution (ch ...
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 clas ...
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 ...
terms, orthochromasia refers to maintaining the position of spectral peaks, while metachromasia refers to a shift in wavelength, becoming either
shorter or
longer
"Longer" is a song written and recorded by the American singer-songwriter Dan Fogelberg and released in 1979 by Full Moon Records and Epic Records. The song can be found on Fogelberg's 1979 album '' Phoenix''. It was also included on his 1982 gre ...
.
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
![15 Hawker Tornado HG641 (15833937541)](https://upload.wikimedia.org/wikipedia/commons/e/ea/15_Hawker_Tornado_HG641_%2815833937541%29.jpg)
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 g ...
that is sensitive to only blue and green light, and thus can be processed with a red
safelight
A safelight is a light source suitable for use in a photographic darkroom. It provides illumination only from parts of the visible spectrum to which the photographic material in use is nearly, or completely insensitive.
Design
A safelight usua ...
. 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 color ...
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
In organic chemistry, an aromatic amine is an organic compound consisting of an aroma ...
-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
Erythrosine, also known as Red No. 3, is an organoiodine compound, specifically a derivative of fluorone. It is a pink dye which is primarily used for food coloring. It is the disodium salt of 2,4,5,7-tetraiodofluorescein. Its maximum absorbanc ...
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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