  We report methods for correcting the photoluminescence emission and
excitation spectra of highly absorbing samples for re-absorption and inner
filter effects. We derive the general form of the correction, and investigate
various methods for determining the parameters. Additionally, the correction
methods are tested with highly absorbing fluorescein and melanin (broadband
absorption) solutions; the expected linear relationships between absorption and
emission are recovered upon application of the correction, indicating that the
methods are valid. These procedures allow accurate quantitative analysis of the
emission of low quantum yield samples (such as melanin) at concentrations where
absorption is significant.
