Relative cone sensitivity measurements were made from 420 mμ to 700 mμ in the spectrum using 42 minute and 3 minute diameter test-light fields in the fovea and a 42 minute diameter field at 10° in the periphery. The data were analyzed with reference to (a) the suggestion that the humps found in the blue region of the spectrum result from the absorption of macular pigment, (b) changes in the over-all shape of the sensitivity function, and (c) the number of humps in the sensitivity function. Two humps were found below 500 mμ in the fovea, one in the orange, and possibly two or three between 500 mμ and 580 mμ. Consideration of the possible origin of the humps favored the conclusion that the humps in the blue region of the spectrum were contributed to by cone activity, since measurements at 10° in the periphery, where there is no pigment, produced an exaggerated hump in the blue below 470 mμ which could only be ascribed to cone activity. Systematic changes in the shape of the functions indicated little change in the long wavelength portion of the curves over the three stimulus conditions, but sizable changes in the relative sensitivity to the short wavelengths. The 10° periphery is increasingly more sensitive than the fovea as wavelengths become shorter than 520 mμ, while the 42′ foveal area is appreciably more sensitive than the 3′ area to blue wavelengths.
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