The Brain Adaptation to the Color of Illumination and not the Retinal Adaptation to the Color of Objects that Determines the Color Appearance of an Object in the Space

Mepean

2018

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The color appearance of negative afterimages was measured by the elementary color naming method, and the results were compared with those obtained by the two‐room technique. Twenty adapting stimuli were presented on a display sequentially. Subjects first assessed the color appearance of the stimuli. After looking at the adapting stimulus for 10 seconds, the subjects assessed color of the afterimage. Apparent hue of the afterimage was in general not opponent color to the adapting color. The relation between the adapting stimuli and the afterimages was analyzed by the angle difference Δθ, when apparent hues are expressed by the angles of the points on the polar diagram of the opponent color theory. The relation relationship of Δθ to the angle of the adapting color θing was quite similar to the results obtained by the two‐room technique, implying that the chromatic adaptation shown by the afterimage also occurs in the brain rather than in the retina.

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Color appearance of afterimages compared to the chromatic adaptation to illumination

Mepean

2018

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Chromatic adaptation to illumination investigated with adapting and adapted color

2017

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The state of chromatic adaptation was investigated by using the two‐room technique. This technique involves a subject in a room who looks a white board in a separate test room through a window and judges the color of the window using the elementary color naming method. When the subject room is illuminated with a colored light and the test room with a white light, the window appears to be a very vivid color, for which the apparent hue depends on the color of the subject room. The color is referred to as the adapted color. The subject also evaluated the appearance of the illumination color of the subject room, which is called the adapting color. Two types of illuminating light in the subject room, fluorescent lamps with 7 colors and LED lamps with 19 colors, were employed. The adapting and the adapted colors were plotted on a polar diagram that was used in the opponent color theory, from which the hue angles were obtained. The hue angle difference between the two colors did not appear to be 180° except for one pair of adapting and the adapted colors, which implies that chromatic adaptation does not follow the opponent color concept. An improvement was achieved to explain the results by introducing complementary colors relation between the adapting and adapted color.

Chromatic adaptation in a 2D photograph demonstrated by a D‐up viewer

2018

It is said that we cannot have color constancy in a photograph. The concept of recognized visual space of illumination (RVSI) asserts that chromatic adaptation occurs when one perceives the illumination that is filling a space and not the objects in the space. It predicts then that if one perceives a 3D scene in a photograph, then color constancy will occur in the photograph. In this work, a dimension‐up (D‐up) viewer was developed to perceive a 3D scene on a 2D photograph, and the effect of chromatic adaptation was measured by the color appearance of a gray patch placed at the center of the photograph. Subjects saw the patch as a vivid color when they saw a photograph that had been taken under colored illumination, which is a normal experience in a real space observation. When the color appearance was measured by the elementary color naming method, the amount of chromaticness of the patch in percentage and the apparent hue were very similar to those observed in the 2‐room technique, thus confirming the prediction by the RVSI theory.