Study Of Color Discrimination Characteristics Of Human Vision System Under Different Chromatic Backgrounds

The demand of color quality has been getting high with the development of science and technology and the improvement of the living standard. The modern color-difference formulae are considered to be applied under special conditions. In order to acquire accurate color difference under various environments, it is necessary to study the parametric effect upon the color discrimination characteristics of human vision system (HVS). With the psychophysical visual methods in this study, the color discrimination threshold and suprathreshold color-difference data were obtained around the five CIE color centers to analyze the parametric effect of different background colors on the human color discrimination characteristics, and to compare and evaluate the prediction performances of the typical color-difference formulae.The color discrimination thresholds of the five CIE color centers were measured on the a*b* plane in CIELAB color space using the interleaved staircase method. The fitted chromaticity ellipses were employed to analyze the influence of background color to the color discrimination characteristics at the threshold level. The data analysis indicated that the local vision uniformity of the five color centers changed with the consistent trend to that for the hue angle of the background color. When the background color was the same as the color center, the highest sensitivity of HVS was achieved, which verified the crispening effect.Based on the principle of the constant stimuli method, the visual data of small suprathreshold color difference were accumulated at the five CIE color centers. Detailed analysis of the experimental results implied that the local vision uniformity of the five color centers generally remained stable. For the gray, yellow and blue centers, the change of the local vision uniformity was along the same tendency as the hue angle of background color. However, the background color hardly affected the local vision uniformity at the red and green centers. The crispening effect was also validated in the range of small suprathreshold color difference, but it was not so remarkable as that in the case of color discrimination threshold.The visual data sets of color discrimination threshold and suprathreshold color difference were employed to test and compare the performances of the typical color-difference formulae, namely, CIELAB, CMC(l:c), CIE94, CIEDE2000, DIN99d, CAM02-SCD, and CAM02-UCS. It is shown that the two color-difference formulae based on the latest color appearance model of CIECAM02 outperformed all other ones, i.e., CAM02-SCD and CAM02-UCS could satisfactorily predict the visual results at the levels of color discrimination threshold and small suprathreshold color difference under the different background colors.