Corresponding chromaticities for different states of adaptation to complex visual fields.

While each of his or her two eyes was independently adapted to a different illuminant in viewing a complex visual field, each of a number of observers matched a series of test colors seen by one eye with a juxtaposed variable stimulus seen by the other eye. The 2 degrees test and matching stimuli were located centrally in the complex adapting field, which subtended an angle of 31 degrees X 24 degrees. In making the matches, the observer viewed the test and matching stimuli for a series of brief intervals (approximately 1 sec) while viewing the complex adapting field with normal eye movements. Nine experiments were performed with different pairs of illuminants and different illuminances ranging from that of an average living room to that of a scene illuminated with hazy sunlight. In three other experiments each of the observer's two eyes was adapted to a different illuminance of D55. The amount of adaptation was more nearly complete at high levels of illuminance than at low levels, and the proportional amount of adaptation was less for the "blue" receptors. When adaptation coefficients were determined from the actual adaptation differences (e.g., from corresponding tristimulus values for matching neutrals) rather than from the adapting illuminants, a linear von Kries transformation based on experimentally determined visual primaries gave corresponding chromaticities that were in good agreement with the results obtained in each of the chromatic-adaptation experiments, except at the lowest illuminances. The results of the experiments in which each eye was adapted to different levels of the same illuminant indicated again that adaptation to the different levels was incomplete, the proportional amount of adaptation being less at low illuminances and for the "blue" receptors. This caused a change in chromatic adaptation with the level of illuminance even when the chromaticities of the adapting lights were equal. The results of these experiments also indicated that higher purities are needed in order to produce the same absolute color appearances at low levels of illuminance.