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The four pigments in a bird's cone cells (in this example, estrildid finches) extend the range of color vision into the ultraviolet. [1]Tetrachromacy (from Greek tetra, meaning "four" and chroma, meaning "color") is the condition of possessing four independent channels for conveying color information, or possessing four types of cone cell in the eye.
The Ishihara test is a color vision test for detection of red–green color deficiencies. It was named after its designer, Shinobu Ishihara, a professor at the University of Tokyo, who first published his tests in 1917. [2] The test consists of a number of Ishihara plates, which are a type of pseudoisochromatic plate.
An Ishihara test image as seen by subjects with normal color vision and by those with a variety of color deficiencies. The main method for diagnosing a color vision deficiency is in testing the color vision directly. The Ishihara color test is the test most often used to detect red–green deficiencies and most often recognized by the public. [1]
A remote vertebrate ancestor of primates possessed tetrachromacy, [1] but nocturnal, warm-blooded, mammalian ancestors lost two of four cones in the retina at the time of dinosaurs. Most teleost fish , reptiles and birds are therefore tetrachromatic while most mammals are strictly dichromats , the exceptions being some primates and marsupials ...
Some invertebrates, such as the mantis shrimp, have an even higher number of cones (12) that could lead to a richer color gamut than even imaginable by humans. The existence of human tetrachromats is a contentious notion. As many as half of all human females have 4 distinct cone classes, which could enable tetrachromacy. [25]
In 2009, adult dichromatic squirrel monkeys were converted into trichromats using gene therapy. [6] New world monkeys are polymorphic in their M-opsin, such that females can be trichromatic, but all males are dichromatic. [6] Recombinant AAV vector was used to deliver a human L-opsin gene subretinally.
The first gives more information about Tetrachromacy than the Tetrachromacy article, (i.e. "each additional type of cones interacts with the other types of cones in such a way that an addition of a new type of cone means an organism can see 100 times as many colours"), however the Tetrachromacy article implies that "Susan Hogan" doesn't exist ...
Colorimetry is "the science and technology used to quantify and describe physically the human color perception". [1] It is similar to spectrophotometry, but is distinguished by its interest in reducing spectra to the physical correlates of color perception, most often the CIE 1931 XYZ color space tristimulus values and related quantities.