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IMMEDIATE PIGMENT DARKENING: VISUAL AND REFLECTANCE SPECTROPHOTOMETRIC ANALYSIS OF ACTION SPECTRUM
Author(s) -
Rosen Cheryl F.,
Jacques Steven L.,
Stuart Mary E.,
Gange Richard W.
Publication year - 1990
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1990.tb01969.x
Subject(s) - wavelength , reflectivity , ultraviolet , extrapolation , pigment , radiation , visible spectrum , optics , chemistry , irradiation , materials science , optoelectronics , physics , mathematics , mathematical analysis , organic chemistry , nuclear physics
Immediate pigment darkening (IPD) occurs in human skin upon exposure to ultraviolet‐A and visible radiation. The spectral changes that occur during IPD were measured with a rapid scanning reflectance spectrophotometer (RS) which employs optical fiber bundles for delivery and detection of light between 400 and 750 nm. The radiation dose dependence and wavelength dependence (334–549 nm irradiation) of IPD were studied by both the classical visual grading method and by spectrophotometric scoring using the RS system. The spectral changes that occur at long wavelengths with IPD mimic the natural absorption spectrum of melanin. Therefore, the IPD was scored in terms of the apparent change in melanin optical density, using the method Kollias and Baqer [Photochem. Photobiol. 43,49–54 (1986)], based on reflectance in the620–720 nm range. The nonlinearity of the visual grading method is demonstrated. The degree of IPD is first‐order with respect to delivered dose and saturates after high doses. The maximum amount of IPD attained at saturation is greater for shorter wavelengths. Extrapolation of the reflectance data suggests the longest wavelength capable of eliciting IPD is about 470 nm.