Vision experiments were conducted recently using NIST Spectrally Tunable Lighting Facility (STLF) to determine quantitatively the most preferred white points across the Planckian locus and the levels of object color saturation (vividness) in a typical interior room setting. Subjects evaluated color appearance of real fruits, vegetables, their skin tones, and the whole room under various light settings. The results showed that the chromaticity below Planckian locus (Duv≈ -0.015) much outside the range of ANSI C78.377 and lights enhancing chroma at a level of C*ab ≈ 5 (Ra≈ 85) on the average are most preferred. These results indicate that the current standards are unduly restricting color quality design, excluding possibilities of more preferred lighting products. The two-metric system in IES TM-30 tries to address this issue but will not be sufficient to meet the needs fully. A color preference metric and additional specifications for preferred white points will be needed to allow development of possible new products that may provide more comfortable or attractive lighting. Needs for such research and future standards work are also discussed in CIE.
