THE WEIGHTING FUNCTION FOR LIGHTNESS IN THE CIE94 COLOR-DIFFERENCE MODEL

We have tested the potential improvement achieved by the CIE94 color-d ifference model [CIE Publication 116-1995] when a linear function of l ightness (SL = K1 + K2 L) is introduced as a weighting function for t he lightness difference Delta L. Our analyses are based on experiment al results previously obtained using object colors and visual colorime ters; new experimental results are not reported here. For the RIT-Dupo nt dataset [Color Res. Appl. 16, 297-316, 1991], the optimal values of the linear function tested are K1 = 1.02; K2 = 0.001, in excellent ag reement with the proposal of the CIE94 model; K1 = 1.0; K2 = 0. Howeve r, for the dataset of Coates et al. [J. Soc. Dyers Colour. 97, 179-183 , 1981], the best predictions were obtained by CMC (l:c) or BFD (l:c). These last values differ by a factor two from the proposal K1 = 1.0; K2 = 0.017 made in another recent study [Color Res. Appl. 19, 273-276, 1994]. Parametric factors, such as the texture of the samples and the lightness of the background, appear to be the main causes of the disc repancies found between the best weighting function for lightness, usi ng different experimental dataset. While new experimental results are reported to clarify this problem, the present results support the prop osal made by th CIE94 model, suggesting that the lightness-dependence correction can be considered as nonrobust and related to local paramet ric effects (C) 1996 John Wiley & Sons, Inc.