G protein-coupled photoreceptor that selectively activates G(i) proteins in response to medium-wavelength (green) light, thereby decreasing intracellular cAMP levels. Activation occurs when the opsin- bound cis-retinal chromophore absorbs a photon and isomerizes to all- trans-retinal, inducing a conformational change in the opsin that triggers a G protein-mediated phototransduction cascade. Mediates visual perception of green light in cone photoreceptor cells. . This is the function of OPN1MW2 (opsin 1, medium wave sensitive 2, Ensembl gene identifier ENSG00000166160).