Skin brightness (L* value)

Method

CIE L* lightness coordinate of skin by reflectance colorimetry with a chromameter or spectrophotometer at a defined site, under the device's stated illuminant and observer geometry. Site and device are recorded on the edge.

The method is part of the endpoint identity. Studies measuring the same quantity by a different method are held as separate endpoints.

Notes

SIGN INVERSION HAZARD with the melanin index measured on the same skin at the same visit by the same or an adjacent device - PMID 33938432 reports both - because this improves by RISING and the melanin index improves by FALLING, and that paper explicitly notes the mismatch. Distinct also from the a* (redness/erythema) and b* (yellowness) coordinates exported from the SAME colorimeter reading in the same session: separate axes with separate meanings, and a* tracks inflammation rather than pigmentation. Direction of benefit assumes a brightening or depigmentation objective, which is a cosmetic endpoint and should be recorded as such.