The effect of luminance differences on color assimilation

Abstract

The color appearance of a surface depends on the color of its surroundings (inducers). When the perceived color shifts towards that of the surroundings, the effect is called ''color assimilation'' and when it shifts away from the surroundings it is called ''color contrast.'' There is also evidence that the phenomenon depends on the spatial configuration of the inducer, e.g., uniform surrounds tend to induce color contrast and striped surrounds tend to induce color assimilation. However, previous work found that striped surrounds under certain conditions do not induce color assimilation but induce color contrast (or do not induce anything at all), suggesting that luminance differences and high spatial frequencies could be key factors in color assimilation. Here we present a new psychophysical study of color assimilation where we assessed the contribution of luminance differences (between the target and its surround) present in striped stimuli. Our results show that luminance differences are key factors in color assimilation for stimuli varying along the s axis of MacLeod-Boynton color space, but not for stimuli varying along the l axis. This asymmetry suggests that koniocellular neural mechanisms responsible for color assimilation only contribute when there is a luminance difference, supporting the idea that mutual-inhibition has a major role in color induction. Color contrast Color contrast has been reported under a wide range of spatiochromatic conditions: unconstrained, when there are luminance and color differences between the target and the inducer (Monnier & Shevell,

Large enhancement of simultaneous color contrast by white flanking contours

“…Monnier and Shevell showed that color shifts were observed only for the S-cone color direction 25,29 , while other studies have found that the effect also occurred along the L-M cone color direction but with smaller illusory effects 7,28 . Our illusion under the white-contour condition using the red-cyan color configuration, was as strong as the Monnier-Shevell illusion.…”

“…The Monnier-Shevell illusion was reported as color shifts occurring along the short-wavelength cone (S cone) direction 27 . There were reports showing the same illusions along red-cyan colors (long to medium wavelength cone direction; L-M cone), but the magnitude of these effects was smaller 7,28 . Considering that classical color assimilation and contrast emerges across all hues 3 , it is questionable that synergistic color shifts are constrained along the S cone axis.…”

“…These color shifts were explained by receptive field organization in which an additive effect arising from a proximal surround and a subtractive effect arising from a distal surround 25,26 . This illusion reflects not only the synergistic effect, but also the luminance contrast of the center 7 . The greater the luminance contrast of the center, the larger color shifts that occur.…”

Instrumental and visual evaluation of the color adjustment potential of resin composites

“…There are two types of color induction: color contrast and color assimilation. Color contrast occurs when the perceived color (the target) shifts away from the surrounding color (the inducer), and color assimilation occurs when the perceived color shifts toward the inducer …”

“…Color contrast occurs when the perceived color (the target) shifts away from the surrounding color (the inducer), and color assimilation occurs when the perceived color shifts toward the inducer. 10,11 In dentistry, the blending effect refers to the interaction of dental materials and hard dental tissues and is manifested by a smaller color difference if they are observed together than if viewed individually. 12 In other words, two colors, seen side by side, will blend under the appropriate circumstances: the perceived color of a region shifts toward the color of the surround.…”