Some aspects of the visual scaling of large colour differences - II

In an earlier article the authors related visually-scaled large colour diff erences to Delta E* values calculated using four colour-difference formulae . All four metrics yielded linear regressions from plots of visual colour d ifference against Delta E*, and Delta E-94* gave the best linear fit, but t he correlations were rather low. In an effort to clarify matters, the previ ous investigation is expanded to include data not hitherto examined. The li nk between visual colour difference and Delta E* colour metrics is further explored in terms of a power law relationship over a wide range of lightnes s, hue, and chroma variations within CIELAB colour space. it is shown that power-law fits are superior to linear regressions in all cases, although co rrelations over lar ge regions of the colour space are not very high. Parti - tioning of the experimental results to give reduced data sets in smaller regions is shown to improve correlations markedly using power-law fits. Con clusions are drawn concerning the uniformity of CIELAB space in the context of both linear and power-law behavior. (C) 2000 John Wiley & Sons, Inc.