Toward adaptation-aware optimization of tunable multi-LED lighting: modeling adaptation-CCT-dependent hue-bin preference targets.

The influence of adaptation correlated color temperature (CCT) on preferred local chroma and hue shifts is investigated across four TM-30 hue bins (j ∈ {1, 4, 6, 12}: red, yellow, green, blue). Fifty-two observers at Wuhan University evaluated ecologically valid, multi-object stimuli using the dual-lighting design of the preceding paper, which independently controls adaptation and object illumination, across a 9 × 11 grid of chroma-hue shift combinations at three adaptation CCTs (Tcp ∈ {3200, 4500, 6500 K}) and constant illuminance (Ev=500 lx). Bin-wise bivariate Gaussian surfaces were fitted to pooled ratings, capturing preference location and anisotropy; preferred shift centroids were estimated via bootstrapping and modeled with log-linear functions of ln(Tcp). Unlike the previously reported monotonic chroma compression with increasing illuminance, the direction of the CCT effect is hue-bin-dependent: preferred chroma shifts increase with CCT in bins 1, 4, and 6, while bin 12 (blue) shows the opposite trend. All pairwise CCT comparisons are statistically significant (Hotelling's T2, p < 0.001). A secondary, exploratory comparison enabled by the single shared condition (500 lx, 4500 K) shows statistically significant differences between the present dataset and the earlier German dataset in all four bins (p ≤ ~0.001), with the largest effects in bin 1 (hue-shift direction inversion, Δh' = -7.78, ΔE' = 16.07) and bin 12 (chroma preference divergence, ΔC' = -8.17, ΔE' = 10.25); differences in bins 4 and 6 are statistically significant but perceptually minor (ΔE' ≤ ~4.18). Because the two datasets come from different laboratories, lighting systems, and realized SPDs, and partly from different object sets, these differences cannot be unambiguously attributed to culture and are reported as a bounded, preliminary observation rather than a controlled cross-cultural test. The resulting CCT-dependent preferred-shift functions complement the illuminance-dependent functions of the preceding paper and provide input for an adaptation-integrated color-preference index.