Perceived surface color in binocularly viewed scenes with two light sources differing in chromaticity

Area of Science:

• Visual perception
• Color science
• Computational modeling

Background:

• Color constancy is crucial for visual perception, enabling stable color recognition under varying illumination.
• Surface orientation affects the spectral composition of light reaching the observer, posing a challenge for color constancy.

Purpose of the Study:

• To investigate how perceived surface orientation impacts the perceived color of matte surfaces.
• To determine the extent to which observers discount orientation when judging surface color under complex lighting conditions.

Main Methods:

• Observers adjusted a test patch's color to appear achromatic under dual illumination (blue diffuse, yellow punctate).
• Orientation was manipulated, and observers estimated it using a gradient probe.
• An equivalent illuminant model was developed to analyze observer performance.

Main Results:

• Achromatic settings varied significantly with perceived surface orientation.
• Observers exhibited partial discounting of orientation, failing to fully compensate for its effect on perceived color.
• Observer errors in estimating light source direction and chromaticity explained the partial discounting.

Conclusions:

• Perceived orientation is a significant factor in color perception, even under controlled lighting.
• Visual system's color constancy mechanism shows limitations in discounting orientation effects.
• Errors in estimating illuminant properties contribute to failures in color constancy.