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Annette Werner, Lindsay T. Sharpe; The spatial tuning of chromatic adaptation. Journal of Vision 2002;2(7):547. doi: 10.1167/2.7.547.
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© ARVO (1962-2015); The Authors (2016-present)
A central issue for understanding chromatic adaptation is the influence of the spatial complexity of a scene. In previous experiments, we found that the early time-course (0.2–5 sec) of mid-spectral chromatic adaptation is accelerated by a cortical mechanism that responds to contrast in the adaptation-pattern (Werner et al., Vis. Res., 2000 (40): 1101–1113). Our new experiments investigate the properties of this spatial component of chromatic adaptation. The pattern (15.4 × 13.2 deg) was presented on a calibrated colour monitor and consisted of either hexagonal patches or horizontal stripes of different luminances. For the reference condition, ite was achromatic (u′ = 0.197, v′ = 0.468; Lmean = 19.3cd/m2). Chromatic adaptation was measured for the transition from D65 adaptation to a 5s green adaptation-light located in an equiluminant plane in colour space (chromaticities were chosen from cardinal axes after Krauskopf et al., 1982). The effect of chromatic adaptation was measured by a hue cancellation technique, which involved maintaining the achromatic appearance of a central hexagonal test-patch (2.2 × 2.4 deg). Our results show that mid-wavelength adaptation is a function of the magnitude of luminance contrast in the adaptation-pattern, indicating the influence of a mechanism of contrast gain control acting on chromatic adaptation. Furthermore, the contrast component of adaptation responds to the spatial complexity of the adaptation pattern rather than to local contrast per se, indicating a global rather than local mechanism. Finally, chromatic adaptation is selective for the spatial frequency and orientation of the adaptation pattern. The results are interpreted in terms of spatial adaptation gain control and as evidence for the co-processing of form and colour information at a cortical level. A possible relation to contrast gain mechanisms is discussed. This study was supported by DFG SFB 430, Tp A7.
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