Abstract
Natural lighting environments can dramatically differ depending on location, time, or weather conditions. Here we tested the degree to which humans can simultaneously judge color and gloss of objects under diverse lighting environments. We selected 12 image-based environmental illuminations captured under different weather conditions (sunny and cloudy) and locations (indoor and outdoor) and applied two manipulations to each illumination to expand the diversity: (i) rotating the chromatic distribution by 90 degrees to generate chromatically atypical environments and (ii) scrambling phase in the frequency domain to make the lighting geometry unnatural. Under each of 36 environments, we used a physics-based renderer to generate a test image from a single 3D mesh of a random everyday object that was assigned random color and specularity. In a different lighting environment, we separately rendered a comparison image containing a bumpy object. In each trial test and comparison images were presented side-by-side on a computer screen, and participants were asked to adjust color (in lightness, hue and chroma) and specularity of the comparison object until it appeared to be made of the same material as the test, shown in a different lighting environment. Results showed that hue settings were highly correlated with ground-truth values for natural and phase-scrambled lighting conditions, but the accuracy of the settings worsened in chromatically atypical environments. Chroma and lightness constancy were generally poor, but these failures correlated with simple image statistics such as mean chroma and mean lightness over the object region. Gloss constancy was limited especially under diffuse lighting (e.g. cloudy environments). Constancy errors had high consistency across participants. These results suggest that though color and gloss constancy hold well in many situations, some properties in lighting environments such as chromatic unfamiliarity or diffuseness potentially hamper our stable visual judgements of material properties.