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Difference spectra of the visual pigments have been measured in single rods and cones of a parafoveal region of the human retina. Rods display an absorption maximum (lambdamax) at about 505 mmicro associated with rhodopsin. Three kinds of cones were measured: a blue-sensitive cone with Amaxe about 450 mpf; two green-sensitive cones with Xmaa about 525 mumicro; and a red-sensitive cone with lambdamax about 555 mmicro These are presumably samples of the three types of cone responsible for human color vision.
Brown et al. (Fri,) studied this question.