Chromatic discrimination with variation in chromaticity and luminance: data and theory.
Boynton and Kambe developed a model of chromatic discrimination in which thresholds are mediated by two independent mechanisms: the short-wavelength sensitive (S-) cones (S-cone axis), and the middle-wavelength sensitive (M-) and long-wavelength sensitive (L-) cones (M/L-cone axis). In this study, we used a Maxwellian view optical system to investigate fundamental properties of the model as a function of chromaticity and luminance. We confirmed that discriminations along the S-cone axis were dependent on S-cone excitation level. However, changes in chromaticity and changes in mean luminance were not described by a single threshold-vs-radiance (TVR) template. We developed a model to account for the different effects of changing S-cone excitation by varying mean chromaticity and by varying mean luminance. M/L-cone discriminations showed a minimum at the L-cone excitation to white, indicating strong opponency. The thresholds increased with luminance approaching a Weber region and showing parallel functions for differing chromaticities. These data are fit by a model allowing retinal gain controls and spectral opponency.
Yeh
T
T
Visual Sciences Center, University of Chicago, IL 60637.
Pokorny
J
J
Smith
V C
VC
D000328:Adult; D003118:Color Perception / Q000502:physiology*; D004192:Discrimination, Psychological / Q000502:physiology; D006801:Humans; D008433:Mathematics; D008959:Models, Neurological; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology; D012684:Sensory Thresholds / Q000502:physiology; D013053:Spectrophotometry