Reduces benzil stereospecifically to (S)-benzoin. Is probably involved in a pathway contributing to genomic integrity. (S)-benzoin + NADP(+) = benzil + H(+) + NADPH By single-strand DNA damage. Displays increased levels of spontaneous RAD52 foci in proliferating diploid cells. Present with 1620 molecules/cell in log phase SD medium. Belongs to the short-chain dehydrogenases/reductases (SDR) family.