Repository logo

Scotopically equated stimuli versus photopically equated stimuli in unique hue judgments




Douda, Nathaniel D., author
Volbrecht, Vicki J., advisor
Nerger, Janice L., committee member
Draper, Bruce, committee member
Dik, Bryan, committee member

Journal Title

Journal ISSN

Volume Title


One of the quandaries when studying color perception in the peripheral retina is whether to equate stimuli photopically to the cones or scotopically to the rods. Both methods are prevalent in the literature and while many of the findings are similar when using either method, there are some notable differences. The purpose of this study was to determine whether the differences in results can be at least partially attributed to the methodology used to equate experimental stimuli. Unique hue loci (blue, green, yellow) were measured in the fovea and at 10° temporal retinal eccentricity under bleach and no-bleach conditions for stimuli equated either photopically (0.3 and 2.3 log phot td) or scotopically (1.0 and 3.0 log scot td). While some differences in unique hue loci exist depending on the method of equating stimuli, the overall pattern of results suggested that different conclusions cannot be drawn depending on the method of equating stimuli. Most likely, the differences reported among unique hue studies are not due to the method of equating stimuli. The findings from this study suggest the method used to equate stimuli can be discounted as a potential confound in interpretation of results from unique hue studies.


Rights Access


unique hues
color vision
photopically equated


Associated Publications