Angle resolved color of bulk scattering media

Area of Science:

• Color Science
• Optical Engineering
• Human Visual Perception

Background:

• The angular dependence of light reflectance significantly impacts the perceived color of matte surfaces.
• Understanding these angular color variations is crucial for accurate color reproduction and material characterization.

Purpose of the Study:

• To investigate the angular dependence of the reflectance factor and resulting color differences in matte samples.
• To evaluate the effectiveness of angle-dependent chromatic adaptation strategies in minimizing perceived angular color variations.
• To explore the role of reference white selection in reducing observed lightness and chroma differences.

Main Methods:

• Measurements of angle-resolved reflectance factor using a goniophotometer.
• Simulations based on radiative transfer theory to model reflectance behavior.
• Translation of spectral data to CIELAB color coordinates for quantitative analysis.

Main Results:

• Both measurements and simulations confirmed a characteristic dependence of reflectance factor on observation angle.
• Significant angular color differences were observed when translating reflectance spectra to CIELAB coordinates.
• Angle-dependent chromatic adaptation, particularly with a non-absorbing opaque reference white, reduced angular color differences.
• Using undyed paper as a reference white further reduced angular lightness differences, but chroma differences remained substantial.

Conclusions:

• Perceived color variations with viewing angle are significant and linked to reflectance properties.
• Angle-dependent chromatic adaptation offers a viable method for mitigating perceived angular color shifts.
• Human visual system's sensitivity to chroma changes may contribute to the persistence of angular color differences even after adaptation.