Haisong XU,^1,2 Hirohisa YAGUCHI¹ and Satoshi SHIOIRI¹

¹Department of Information and Image Sciences, Chiba, University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 Japan, ²State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027 China

(Received December 26, 2000; Accepted February 14, 2001)

The advanced color-difference formulae, CMC, CIE94, and the recently proposed CIEDE2000 formula, together with the basic CIELAB system, were estimated using the chromaticity discrimination threshold data at CIE Gray and Blue color centers. Gray is the most basic color and blue is, perceptually, in the most different region from other areas across the color space. The test stimuli, evenly distributed in the (a^*, b^*)-, (a^*, L^*)-, and (b^*, L^*)-plane of the CIELAB space, were generated on a CRT display, driven by a VSG system. Each direction from each color center was assessed 3 times by a panel of 9 normal color-vision observers with the psychophysical method of interleaved staircase. The experimental data were reliable and consistent with other studies according to the observer accuracy and fitted ellipse parameters. A comprehensive analysis shows the color discrimination tolerances could be well fitted by ellipses, and the CIEDE2000 and CIELAB formulae performed better than CIE94 while the CMC worst at the threshold level for the color centers studied.

Key words : color difference, color-difference formula, color discrimination threshold, CRT, method of staircase, chromaticity discrimination ellipse, CIELAB color space

hsxu@vision.tp.chiba-u.ac.jp