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Аннотация A method is outlined by which the parameters governing light-induced charge transfer processes in photorefractive crystals can be determined. The system BaTiO3 : Rh is treated as an example. EPR is used to obtain information on the EPR-active defect charge states. By simultaneous observation of light-induced EPR- and optical absorption changes the corresponding optical absorption bands are established as fingerprints of the defect charge states. Consistency arguments allow to label also EPR-silent absorption bands in this way, significantly extending the scope of EPR based defect studies. On this basis the charge transfer paths taking place under illumination are identified. Quantitatively, the defect concentrations are directly on indirectly derived from the available EPR signals. In addition the kinetics of the light-induced changes of the densities of the occurring defect charge states are studied. In conjunction with the defect concentrations, this allows to deduce the responsible transfer parameters.