Color appearance shift in augmented reality metameric matching.

The physical additivity of optical-see-through (OST) augmented reality (AR), where display and the real-world overlay with each other, impacts its color appearance. We explored this unique dynamic by looking at the effect of background correlated color temperature (CCT) on AR color appearance with a color matching experiment between a prototype OST-AR RGB system and daylight spectrum reproduction. Different background CCT, luminance levels, and two stimulus types [simulated two-dimensional (2D) disk and three-dimensional (3D) cube] were examined. We found that when the background color is inconsistent with the stimulus providing conflicted cues, matched colors in AR shifted towards the background. The luminance matched on the 3D cube is higher than the 2D disk, suggesting the impact of context on the AR appearance. A controlled metameric matching group between daylight reproduction and LCD or CRT did not show the shift, indicating that the appearance shift is not due to the RGB-spectrum metameric matching, but due to RGB foreground-spectral background interaction beyond simple additivity. How perceptual weighting on the foreground and background is modified to predict the appearance as a function of additivity is discussed.

Properties of lateral interaction in color and brightness induction.

In a visual scene, when objects are surrounded by other components, neural mechanisms increase the perceived color and brightness difference between an object and its surround, potentially enhancing an observer's ability to segment objects. Despite almost two centuries of empirical investigations, the nature of induction mechanisms remains elusive. To elucidate the nature of these mechanisms, we introduce a new method for measuring color and brightness induction that allows separate manipulation of lateral interactions and adaptation, and controls for eye-movement-related effects. We use the method to examine the function relating induction magnitude to contrast change in the surround, the symmetry of induction in complementary directions for the three cardinal color axes, and the effect of blur between the test and the surround. On average, brightness induction was more linear than chromatic induction. The induction magnitude was similar for surrounds of complementary colors on average and for many conditions, and when individual observers deviated from symmetry it could be on either side. Edge blur did not change the induction magnitude. For slower presentations, light/dark induction increased to further reduce asymmetry, suggesting that previously found light/dark induction asymmetry is not due to lateral interactions or prolonged adaptation. Lateral interactions underlying induction are thus mostly symmetric for color and brightness axes and involve spatially opponent filters of modest widths, rather than edge extraction.

Factors governing the speed of color adaptation in foveal versus peripheral vision.

Troxler showed that fixated stimuli fade faster in peripheral than in foveal vision. We used a time-varying procedure, to show that peripheral adaptation is faster and more pronounced than foveal adaptation for the three cardinal color modulations that isolate different classes of retinal ganglion cells. We then tested the hypothesis that fixational eye movements control the magnitude and speed of adaptation, by simulating them with intermittent flashes, and attenuating their effects with blurred borders. Psychophysical and electrophysiological results confirmed the eye movement-based hypothesis. By comparing effects across classes of ganglion cells, we found that the effects of eye movements are mediated not only by the increase in size of receptive fields with eccentricity, but also by the sensitivity of different ganglion cells to sharp borders and transient changes in the stimulus. Finally, using the same paradigm with retinal ganglion cells, we show that adaptation parameters do not vary for the three classes of ganglion cells for eccentricities from 2° to 12°, in the absence of eye movement.

Troxler fading, eye movements, and retinal ganglion cell properties.

We present four movies demonstrating the effect of flicker and blur on the magnitude and speed of adaptation for foveal and peripheral vision along the three color axes that isolate retinal ganglion cells projecting to magno, parvo, and konio layers of the LGN. The demonstrations support the eye movement hypothesis for Troxler fading for brightness and color, and demonstrate the effects of flicker and blur on adaptation of each class of retinal ganglion cells.

Hue discrimination, unique hues and naming.

The hue discrimination curve (HDC) that characterizes performances over the entire hue circle was determined by using sinusoidally modulated spectral power distributions of 1.5 c/300 nm with fixed amplitude and twelve reference phases. To investigate relationship between hue discrimination and appearance, observers further performed a free color naming and unique hue tasks. The HDC consistently displayed two minima and two maxima; discrimination is optimal at the yellow/orange and blue/magenta boundaries and pessimal in green and in the extra-spectral magenta colors. A linear model based on Müller zone theory correctly predicts a periodical profile but with a phase-opponency (minima/maxima at 180° apart) which is inconsistent with the empirical HDC's profile.