Color perception test
|Color perception test|
Example of an Ishihara color test plate. The number "74" should be clearly visible to viewers with normal color vision. Viewers with dichromat or anomalous trichromat may read it as "21", and viewers with achromat may see nothing.
The Ishihara Color Test is an example of a color perception test for red-green color deficiencies. It was named after its designer, Dr. Shinobu Ishihara, a professor at the University of Tokyo, who first published his tests in 1917.
The test consists of a number of colored plates, called Ishihara plates, each of which contains a circle of dots appearing randomized in color and size. Within the pattern are dots which form a number or shape clearly visible to those with normal color vision, and invisible, or difficult to see, to those with a red-green color vision defect, or the other way around. The full test consists of 38 plates, but the existence of a deficiency is usually clear after a few plates. There is also the smaller test consisting only 24 plates.
The plates make up several different test designs:
- Transformation plates: individuals with color vision defect should see a different figure from individuals with normal color vision.
- Vanishing plates: only individuals with normal color vision could recognize the figure.
- Hidden digit plates: only individuals with color vision defect could recognize the figure.
- Diagnostic plates: intended to determine the type of color vision defect (protanopia or deuteranopia) and the severity of it.
See also 
- S. Ishihara, Tests for color-blindness (Handaya, Tokyo, Hongo Harukicho, 1917).
- Ishihara color test information
- The Ishihara Color Blindness Test
- Test of color blindness with the indication of the weaknesses in various colors, quantifies green red blue deficiency (ISHIHARA test alternative)
- Flash animated Ishihara color blindness test