The first action spectra for erythema and delayed pigmentation in human skin were determined 90 years ago by Karl Hausser and Wilhelm Vahle in Germany, and since then a number of studies have been undertaken to redefine these action spectra. In this paper we give an overview of the action spectra for erythema and pigmentation that have been published during this 90-yr period, as well as indicating their uncertainties and shortcomings.
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