A rhodopsin-like G-protein coupled receptor that is a translation product of the human OPN1LW, OPN1MW, OPN1SW, RHO, OPN3, OPN4, or OPN5 genes, 1:1 orthologs thereof, or a semi-ortholog thereof in Metazoa. The active form binds a vitamin A-based retinaldehyde chromophore through a Schiff base linkage to a Lys residue in the seventh transmembrane alpha helix. [ PRO:WCB PRO:XQ http://en.wikipedia.org/wiki/Opsin ]