An investigation of the colors in the Munsell 5R plane and an extension of this study to colors produced in a small aperture in a large white illuminated surround have led to the discovery of some interesting and novel relationships. It is found that under these conditions the domain of surface color perception includes the whole of the range from V=0 to 10 and pc= 0 to 1.0 and under some conditions more. For a color of a given dominant wavelength there is a locus lying wholly within this space along which lie colors that do not appear to contain gray. If luminance or purity is increased above a point on this line, the sample takes on the appearance characteristic of a fluorescent material. If either is decreased below a point on this line, the color is perceived as having a gray component added to the purely chromatic component in increasing amounts until at pc=0, there is no chromatic component perception of the color or at low values of V the sample appears black. Above a point somewhat higher than surround luminance, the appearance of fluorescence ceases and the surface mode changes to the illuminant mode, the saturation of the perceived color decreasing with increasing luminance above this point. An hypothesis is suggested to explain the facts and it is pointed out that more than one kind of "brightness" is necessarily involved.
RALPH M. EVANS, "Fluorescence and Gray Content of Surface Colors," J. Opt. Soc. Am. 49, 1049-1058 (1959)