Chromatic discrimination of natural objects

Abstract

Studies of chromatic discrimination are typically based on homogeneously colored patches. Surfaces of natural objects, however, cannot be characterized by a single color. Instead, they have a chromatic texture, that is, a distribution of different chromaticities. Here we study chromatic discrimination for natural images and synthetic stimuli with a distribution of different chromaticities under various states of adaptation. Discrimination was measured at the adaptation point, where the mean chromaticity of the test stimuli was the same as the chromaticity of the adapting background, and away from the adaptation point. At the adaptation point, discrimination for natural objects resulted in threshold contours that were selectively elongated in a direction of color space matching the chromatic variation of the colors within the natural object. Similar effects occurred for synthetic stimuli. Away from the adaptation point, discrimination thresholds increased and threshold ellipses were elongated along the contrast axis connecting adapting color and test color. Away from the adaptation point, no significant differences between the different stimulus classes were found. The effect of the chromatic texture on discrimination seemed to be masked by the overall increase in discrimination thresholds. Our results show that discrimination of chromatic textures, either synthetic or natural, differs from that of simple uniform patches when the chromatic variation is centered at the adaptation point.

Parallel, multi-stage processing of colors, faces and shapes in macaque inferior temporal cortex

“…Color stimuli were generated in DKL color space 26 , and calibrated using spectral readings taken with a PR-655 spectroradiometer (Photo Research Inc., Chatsworth, CA) using procedures developed by Thorsten Hansen (personal communication). The spectra were multiplied with the Judd-revised Commission Internationale de l’Eclairage (CIE) 1931 color matching functions to derive CIE xyY coordinates of the monitor primaries 51 , and cone excitation was calculated using the Smith and Pokorny cone fundamentals 52 . Twelve color directions were chosen, evenly sampling the azimuth of the equiluminant plane of DKL space (Figure 2a, Supplementary Figure 3).…”

Textures as Probes of Visual Processing

“…First, while we focus here on grayscale images, the notion of image statistics and therefore visual texture extends immediately to chromatic and even hyperspectral images. The variety of image statistics is now much greater, as each pixel is represented by a list of scalars (one for each chromatic or spectral channel), rather than by a single grayscale value (Hansen et al 2008, Li & Lennie 1997, te Pas & Koenderink 2004). Similarly, the notion of a static visual texture extends to that of a texture movie: the image is an array with two dimensions for space and one for time (Hu & Victor 2010).…”

Texture affects color emotion

“…Nonuniformity of object colors (texture) and their environment seems to be the rule rather than the exception. [9][10][11] Therefore, a logical next step in color emotion studies is the extension from uniform color (UC) toward color texture (CT). So far, the role of texture in color emotion has received only little attention.…”