Scaling Lightness Perception and Differences Above and Below Diffuse White

The first purpose of this thesis was to design and complete psychophysical experiments for scaling lightness and lightness differences for achromatic percepts above and below the lightness of diffuse white (L*=100). Below diffuse white experiments were conducted under reference conditions recommended by CIE for color difference research. Overall a range of CIELAB lightness values from 7 to 183 was investigated. Psychophysical techniques of partition scaling and constant stimuli were applied for scaling lightness perception and differences, respectively. The results indicate that the existing L* and CIEDE2000-weighting functions approximately predict the trends, but don’t well fit the visual data. Hence, three optimized functions are proposed, including a lightness function, a lightnessdifference weighting function for the wide range, and a lightness-difference weighting function for the range below diffuse white. The second purpose of this thesis was to modify the color spaces for highdynamic-range scenes and images. Traditional color spaces have been widely used in a variety of applications including digital color imaging, color image quality, and color management. These spaces, however, were designed for the domain of color stimuli typically encountered with reflecting objects and image displays of such objects. This means the domain of stimuli with luminance levels from slightly above zero to that of a perfect diffuse white (or display white point). This limits the applicability of such spaces to color problems in high-dynamic-range (HDR) imaging. This is caused by their hard intercepts