Dr. Verriest’s valuable addition to the empirical data on age and color discrimination raises questions about sample selection and suggests the desirability of longitudinal follow-up work on the younger age groups. The advisability of treating the discrimination losses produced by selective short-wave absorption as a tritan type of color vision deficiency is questioned (a) on theoretical grounds and (b) because selective filtering never completely mimics congenital color-vision defects. An explanation is suggested for Dr. Verriest’s report that color equations made through selective filters are not those expected on the basis of computed stimulus transmittances. Generalities are sought in his large body of data on diseased eyes and color vision, and the puzzling fact that no color-vision defects are found in about 25% of the diseased cases tested is pointed out.
In contrast to Dr. Boynton’s views concerning color adaptation limits, the linkage between stable color perceptions and extremely labile chromatic adaptation is emphasized. Arguments are presented against his suggestion that the experimental parameters in research on visual thresholds be standardized. The importance of the time variable in visual research is agreed upon. Because of the discrepancies between the spectral sensitivity curves inferred from Stiles’ increment-threshold technique and those derived from the “over-all spectral sensitivity method,” it is suggested that the increment threshold data might more fruitfully be analyzed in terms of the three-variable opponent color response systems which have been shown to cope satisfactorily with a wide variety of other psychophysical data.
Professor Helson’s systematic research on the Bezold spreading effect stimulates further questions requiring experimental answers. There is the possibility that asymmetrical effects, i.e., contrast and assimilation, occur on the two different sides of his test fields, and that differential rates of the two processes may favor one or the other net effect. The use of a matching technique might expose the presence of such asymmetries, and the relevance of retinal light distribution and image spread functions to the limiting conditions for the two effects is suggested.
© 1963 Optical Society of AmericaFull Article | PDF Article
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