Successive contrast involving luminance and purity alterations of the Ganzfeld.

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Abstract
Os (subjects) were adapted to a homogeneous visual field by projecting red light (dominant wavelength 648 m[mu], luminance. 30 ft-L) onto a translucent eye cap. Following chromatic adaptation, homogeneous postadapting fields differing in luminance and/or colorimetric purity were introduced, producing successive contrast. Using an adapting red of purity 1. 00 8 of 10 Os adapted chromatically. With an adapting red of purity. 50 6 of the 10 Os adapted. For either adapting stimulus, post-adapting fields equal to or greater than the colorimetric purity of the red adapting field were perceived as red. Postadapting fields of purity less than that of the adapting field were perceived as complementary blue-green. The luminance of the postadapting field had little effect upon hue. Thus the importance generally attached to luminance parameters in producing chromatic afterimages is not supported.