Retinoids dehydrogenase/reductase with a clear preference for NADP. Displays high activity towards 9-cis, 11-cis and all-trans-retinal. Shows very weak activity toward 13-cis-retinol. Also exhibits activity, albeit with lower affinity than for retinaldehydes, towards lipid peroxidation products (C9 aldehydes) such as 4-hydroxynonenal and trans-2-nonenal (By similarity). Plays an important function in photoreceptor cells to detoxify 4-hydroxynonenal and potentially other toxic aldehyde products resulting from lipid peroxidation (PubMed:19686838, PubMed:22621924, PubMed:17032653). Has no dehydrogenase activity towards steroids (By similarity). all-trans-retinol + NADP(+) = all-trans-retinal + H(+) + NADPH 11-cis-retinol + NADP(+) = 11-cis-retinal + H(+) + NADPH 9-cis-retinol + NADP(+) = 9-cis-retinal + H(+) + NADPH a 4-hydroxynonen-1-ol + NADP(+) = a 4-hydroxynonenal + H(+) + NADPH (E)-non-2-en-1-ol + NADP(+) = (E)-non-2-enal + H(+) + NADPH (Z)-non-6-en-1-ol + NADP(+) = (Z)-non-6-enal + H(+) + NADPH NADP(+) + nonan-1-ol = H(+) + NADPH + nonanal Cofactor metabolism; retinol metabolism. Expressed in the inner segments of the photoreceptor in retina. Deficient mice are fertile and developed normally. Deficient mice exhibit normal retinal function at 6 weeks, but they show increased susceptibility to retinal cell apoptosis of both cone and rod photoreceptors induced by high intensity illumination (PubMed:17032653). All- trans-retinol production in inner and outer segments of the photoreceptor is not affected in deficient mice (PubMed:22621924). Shows clear specificity for the pro-S hydrogen on C4 of NADPH and the pro-R hydrogen on C15 of retinols. Belongs to the short-chain dehydrogenases/reductases (SDR) family.