Interactions between chromatic adaptation and contrast adaptation in color appearance

Area of Science:

• Visual perception
• Color science
• Neuroscience

Background:

• Color appearance is influenced by light adaptation to mean stimulus color and contrast adaptation to color variations.
• These adaptation processes adjust visual sensitivity and interact dynamically.

Purpose of the Study:

• To investigate the interaction between chromatic adaptation and contrast adaptation.
• To understand how adaptation to mean color influences contrast adaptation and vice versa.

Main Methods:

• Examined how chromatic adaptation state depends on time-varying color contrasts.
• Investigated how adaptation to mean color determines stimulus contrasts for contrast adaptation.
• Measured light adaptation levels under static and dynamic chromatic conditions.
• Analyzed effects of flicker rate on color bias and perceived contrast, including response polarization.

Main Results:

• Light adaptation levels are similar for static chromaticity and high-rate temporal modulations (≥0.5 Hz), suggesting linearity and averaging.
• At slower flicker rates, color appearance is biased by the last half-cycle, potentially altering perceived contrast via response polarization.
• Response polarization saturates moderate contrasts along complementary color axes, indicating multiple chromatic mechanisms.
• Chromatic adaptation shows partial adjustment, leaving a residual color bias.
• Contrast adaptation reduces perceived contrast relative to this residual color, not an achromatic point.
• Contrast discrimination thresholds are lower around the residual color than the achromatic point.

Conclusions:

• Chromatic and contrast adaptation interact, with chromatic adaptation influencing contrast perception and vice versa.
• Response polarization at slow flicker rates suggests distinct chromatic mechanisms.
• Measures of 'zero contrast' dissociate under biased chromatic adaptation, indicating separate encoding channels for chromatic contrast.