The effects of habitat structure and lighting on object and background appearance

The color, geometry, and lighting of environments characterize their appearance to humans and other animals and, as a result, play an important role in the evolution of animal coloration. Yet despite this long-standing association, how changes in lighting from atmospheric conditions and three-dimensional geometry interact to alter the appearance of scenes and animals remains largely unexplored. To investigate these interactions, we quantified the appearance of natural backgrounds and standardized targets with color-calibrated photographs and 3-dimensional (3D) scans of 672 natural scenes taken under diffuse and direct lighting conditions. We find several instances where lighting and the local 3D environment systematically altered the colors and patterns of scenes and a target object, as well as their relationship with spatial scale. Shadows formed under direct lighting increased luminance and short-long wave (blue-yellow) contrast across spatial scales, especially at larger spatial scales for habitats with a greater 3D variation. Conversely, medium-long wave (green-red) information was highly stable to changes in lighting. Direct lighting and the 3D environment also influenced the directionality and orientation of patterns within the scenes and targets due to the formation of cast and self-shadows of different orientations. These analyses demonstrate the importance of considering the lighting and geometry of an environment when comparing the statistics of animals and their backgrounds.