G protein-coupled photoreceptor that selectively activates G(i) proteins in response to long-wavelength (red) light, thereby decreasing intracellular cAMP levels (PubMed:2937147, PubMed:6140680, Ref.5). 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 (Ref.5). Mediates visual perception of red light in cone photoreceptor cells (PubMed:12051694, PubMed:8213841, PubMed:8666378). {ECO:0000269|PubMed:12051694, ECO:0000269|PubMed:2937147, ECO:0000269|PubMed:6140680, ECO:0000269|PubMed:8213841, ECO:0000269|PubMed:8666378, ECO:0000269|Ref.5}. This is the function of ENSG00000102076 (OPN1LW, opsin 1, long wave sensitive).