Fig. 9 Human foveal spectral sensitivities of three types of color-defective humans (curves). The data points are from normal subjects made temporarily color defective by immediate previous exposure to intense colored light and follow closely the curves from color-defective humans. The curves and data points probably reflect the spectral sensitivities of three kinds of cone systems. (Data from Willmer EN: A physiological basis for human colour vision in the central fovea. Doc Ophthalmol 9:235, 1955; Blackwell H, Blackwell O: Rod and cone receptor mechanism in typical and atypical congenital achromatopsia. Vision Res 1:62, 1961; Brindley GS: The effects on colour vision of adaptation to very bright lights. J Physiol [London] 122:332, 1953)