We present methods to estimate perceptual uniformity of color spaces and to derive a perceptually uniform RGB space using geometrical criteria defined in a logarithmic opponent color representation.

Neurons in the lateral geniculate nucleus cannot perform the spatial color calculations necessary for color contrast and color constancy. Under neutral-adapting conditions, we mapped the cone inputs (L, M, and S) to 83 cone-opponent cells representing the central visual field of the next stage of visual processing, primary visual cortex (V1), to determine how the color signals are spatially tra...

Using a hue scaling technique, we have examined the appearance of colored spots produced by shifts from white to isoluminant stimuli along various color vectors in order to examine color appearance without the complications of the combined luminance and chromatic stimulation involved in most previous hue scaling studies, which have used flashes of monochromatic light. We also used spots lying a...

Simple visual-reaction times (VRT) were measured for a variety of stimuli selected along red-green (L-M axis) and blue-yellow [S-(L + M) axis] directions in the isoluminant plane under different adaptation stimuli. Data were plotted in terms of the RMS cone contrast in contrast-threshold units. For each opponent system, a modified Piéron function was fitted in each experimental configuration an...

The lateral geniculate nucleus (LGN) is the primary thalamic nucleus that relays visual information from the retina to the primary visual cortex (V1) and has been extensively studied in non-human primates. A key feature of the LGN is the segregation of retinal inputs into different cellular layers characterized by their differential responses to red-green (RG) color (L ⁄M opponent), blue-yellow...

Color processing begins with the absorption of light by cone photoreceptors, and progresses through a series of hierarchical stages: Retinal signals carrying color information are transmitted through the lateral geniculate nucleus of the thalamus (LGN) up to the primary visual cortex (V1). From V1, the signals are processed by the second visual area (V2); then by cells located in subcompartment...

In understanding the basis of the changes in human color vision across eccentricity, one key piece of information remains unknown, whether the relative cone weights of the two cone opponent mechanisms vary. Here we measure detection threshold contours within three planes in a 3-dimensional cone contrast space to reveal the L, M and S-cone weights to the two cone opponent mechanisms, L/M and S/(...

Is there opponency between orientation-selective processes in pattern perception, analogous to opponency between color mechanisms? Here we concentrate on possible opponency in second-order channels. We compare several possible second-order structures: SIGN-opponent-only channels in which there is no opponency between orientations (also called complex channels or filter-rectify-filter mechanisms...

Stimuli varying in intensity and chromaticity, presented on numerous backgrounds, were classified into red/green, blue/yellow and white/black opponent color categories. These measurements revealed the shapes of the boundaries that separate opponent colors in three-dimensional color space. Opponent color classification boundaries were generally not planar, but their shapes could be summarized by...

We have measured how color appearance of squarewave bars varies with stimulus strength and spatial frequency. Observer's adjusted the color of an uniform patch to match the color appearance of the bars in squarewave patterns. We used low to moderate squarewave patterns, from one to eight cycles per degree (cpd). The matches are not photoreceptor matches, but rather are established at more centr...