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.
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“Since the quarrel
Will bear no color for the thing he is,
Fashion it thus: that what he is, augmented,
Would run to these and these extremities.”
—William Shakespeare (1564–1616)
“The perception of the comic is a tie of sympathy with other men, a pledge of sanity, and a protection from those perverse tendencies and gloomy insanities in which fine intellects sometimes lose themselves. A rogue alive to the ludicrous is still convertible. If that sense is lost, his fellow-men can do little for him.”
—Ralph Waldo Emerson (1803–1882)
“The test of a given phrase would be: Is it worthy to be immortal? To “make a beeline” for something. That’s worthy of being immortal and is immortal in English idiom. “I guess I’ll split” is not going to be immortal and is excludable, therefore excluded.”
—Robert Fitzgerald (1910–1985)