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Tanner DeLawyer, Steven Buck, Kevan Kidder, Alex Mills, Amanda Parsons, Amir Shabaneh; The effects of saturation on the perception of brown stimuli. Journal of Vision 2013;13(15):P8. https://doi.org/10.1167/13.15.43.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Early research by Bartleson (1976) established some of the qualitative properties of brown. Among these was the observation that the same long-wavelength stimuli look brown when dim and yellow-orange when bright, relative to surrounding stimuli. One of the other properties that Bartleson had previously observed was that desaturated stimuli appeared browner than saturated stimuli. To test this we used a variety of conditions under which a yellow-orange stimulus would appear desaturated.
Methods: Six observers adjusted the luminance of a constant-chromaticity disk of 2°–7°-diameter (CIE 10° x,y .44, .46), centered either at the fovea or at 7° eccentricity, on a bright white surround (141 cd/m2, CIE 10° x,y .29,.29) in order to define the upper boundary for brown. Thus, the stimulus appeared brown at luminances lower than the boundary and appeared orange-yellow at luminances higher than the boundary. Additionally subjects adjusted an otherwise identical foveal stimulus that had been desaturated through the addition of blue phosphor.
Results: For both foveal and 7° eccentricity conditions, smaller disks were more effective (allowed the subject to perceive brown at higher light levels) than larger disks. Additionally, stimuli presented extra-foveally and desaturated stimuli also produced brown more effectively.
Conclusions: Smaller and eccentric test stimuli are more effective at producing brown than larger or foveal stimuli. This may be because these stimuli appear desaturated as suggested by the increased effectiveness of the desaturatedfoveal stimuli. More research needs to be performed to determine the mechanism through which this desaturation effect is occurring.
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