Aggregate and Category-Level Skin Fidelity Across LED Sources: Evaluating TM-30 Skin Samples with an Expanded Skin-Reflectance Library

ANSI/IES TM-30-24 designates CES #15 and CES #18 as skin-representative color-evaluation samples, summarized by their mean individual fidelity (R_f,CES15,18). This analysis tested how well that two-sample mean represents average fidelity and category-level variation across a 100-spectrum skin-reflectance library stratified into five lightness-defined categories, evaluated across 1,432 architectural LED sources from the DTU PhotoLED database. R_f,CES15,18 closely tracked mean fidelity across the full reference library (r = 0.9976; RMSE = 0.84 Rf points). Benchmarked against all 4,950 possible two-spectrum means from the same library, it exceeded 85.7% of pairs in correlation and 82.7% in RMSE, favorable performance that was not unique. Raw category means within individual sources differed by 4.74 R_f points on average and by as much as 10.66 points. This ordering tracked chroma and was largely captured by the lightness-chroma geometry of the sampled spectra; little category-specific structure remained once that geometry was modeled, and the ordering was not fixed across the two reflectance libraries. Compact subsets were tested under source-only holdout and under simultaneous source-and-skin-spectrum holdout. Greedy selection held a modest source-held-out error advantage over an optimized category-matched random search at 9 to 10 samples. Under simultaneous holdout, subsets of that size preserved source-rank recovery, while reconstruction of unseen category means carried median errors near 1 R_f point. CES #15/#18 therefore serves as a favorable aggregate indicator within this library. Characterizing variation across the sampled skin-reflectance locus requires broader reflectance sets.