Assessing the temporal uniformity of CIELAB hue angle

In recent work [J. Opt. Soc. Am. A 36, 1022 (2019)], we found that ΔE∗ab/s in CIELAB is not suitable for describing the perceived speed of temporal color changes in full-room illumination. Two hue transitions with the same physical speed of change, in terms of ΔE∗ab/s, were not perceived to change at the same speed. This is not really surprising, since CIELAB was not designed to characterize the perception of temporal color transitions in illumination. In this study, we further investigate the temporal uniformity of CIELAB. The stimuli were presented in a square of 4.3° visual angle surrounded by a 4000 K adapting field, similar to the viewing condition for which CIELAB was designed (i.e., where color stimuli are presented on-axis surrounded by a static adaptation field). The human observers viewed pairs of temporal color transitions which were presented sequentially, and were asked to select the one that appeared to change faster. The results confirmed that under these conditions CIELAB was also not temporally uniform. We present preliminary attempts to improve the temporal uniformity for both CIELAB and cone-excitation spaces (i.e., LMS and DKL (Derrington–Krauskopf–Lennie [J. Physiol. 357, 241 (1984)]).