Retinol dehydrogenase with a clear preference for NADP. Oxidizes all-trans-retinol, but seems to reduce all-trans-retinal with much higher efficiency (PubMed:18039331). Has no activity toward steroids (PubMed:18039331). all-trans-retinol + NADP(+) = all-trans-retinal + H(+) + NADPH Cofactor metabolism; retinol metabolism. Localized on the outer side of the inner mitochondrial membrane. Widely expressed (PubMed:18039331). In the retina, detected in the inner segment of the photoreceptor cells. Weak signals are observed in a small population of inner nuclear neurons and the inner plexiform layer (PubMed:12226107). Belongs to the short-chain dehydrogenases/reductases (SDR) family. Was originally thought to lack retinol dehydrogenase (RDH) activity. However, a more recent publication demonstrates a retinol dehydrogenase activity for RDH13.