The spectral sensitivity of the human short-wavelength sensitive cones derived from thresholds and color matches

Abstract

We used two methods to estimate short-wave (S) cone spectral sensitivity. Firstly, we measured S-cone thresholds centrally and peripherally in five trichromats, and in three blue-cone monochromats, who lack functioning middle-wave (M) and long-wave (L) cones. Secondly, we analyzed standard color-matching data. Both methods yielded equivalent results, on the basis of which we propose new S-cone spectral sensitivity functions. At short and middle-wavelengths, our measurements are consistent with the color matching data of Stiles and Burch (1955, Optica Acta, 2, 168-181; 1959, Optica Acta, 6, 1-26), and other psychophysically measured functions, such as pi 3 (Stiles, 1953, Coloquio sobre problemas opticos de la vision, 1, 65-103). At longer wavelengths, S-cone sensitivity has previously been over-estimated.

Human trichromacy revisited

“…2 deviate from the standard trichromatic theory because the observers both have some sensitivity to test lights in the conesilent (Z) direction. However, the conditions of this experiment differed from the conditions used to define the standard color observer (25,26). In particular, the mean illumination is significantly higher and somewhat bluish.…”

“…To show a more complete representation of the data, we plot the thresholds in standard observer color space in Fig. S1 (25,26). In contrast to the trichromatic fits in the fovea, the invisible directions according to the trichromatic fits in the periphery are not in the cone-silent (Z) direction.…”

“…Vienot et al (31) constructed a display apparatus with seven primaries, enabling them to generate cone-silent stimuli that modulate the rhodopsin and melanopsin pigments in human subjects. Basing their calibrations on the standard color observer from Stockman (25,26), and using relatively low light levels, they report significant pupil responses in some individuals but not in others. This observation agrees with our results in that corrections for the individual photopigment characteristics of each observer and for specific light levels are probably required to achieve isolation.…”

“…A particular concern in the healthy human is whether the fourth photopigment might be rhodopsin rather than melanopsin. Including the optics, the estimated peak absorptions of rods and melanopsin-containing cells are 503 nm and 489 nm [using the Stockman-Sharpe photopigment template and lens pigment transmittance function (25); the peak melanopsin absorption without the optics in a nonhuman primate is 482 nm (3)]. Hence, it is virtually impossible to arrange the spectral characteristics of the test light to securely stimulate melanopsin without also stimulating rhodopsin.…”

Heritability of the spatial distribution and peak density of macular pigment: a classical twin study

“…Optical density values were also scaled by a factor of 1.28 in order to compensate for the difference between MP absorbance at 488 and 460 nm. 35 Relative MP optical density (MPD) values were calculated for the horizontal and vertical meridians from the FAF images. The values were then exported into Sigmaplot 7.0 (Systat Software, Inc., Richmond, CA, USA) to plot the MP spatial distribution profile horizontally (SDMP).…”