G protein-coupled photoreceptor that activates the G protein transducin (t) signaling pathway in response to light and is essential for image-forming vision under low-light conditions (PubMed:6140680, PubMed:7846071, PubMed:8107847). Required for postnatal photoreceptor cell viability (PubMed:12566452, PubMed:2215617). Activation occurs when the covalently bound 11-cis-retinal chromophore absorbs a photon and isomerizes to all-trans-retinal, inducing a conformational change in the opsin that triggers G protein-mediated phototransduction (Probable) (PubMed:26200343, PubMed:28753425, PubMed:8107847). Signal termination occurs via receptor phosphorylation, which promotes binding of arrestin (SAG) and displacement of the G protein alpha subunit (Probable) (PubMed:26200343). {ECO:0000269|PubMed:12566452, ECO:0000269|PubMed:2215617, ECO:0000269|PubMed:26200343, ECO:0000269|PubMed:28753425, ECO:0000269|PubMed:6140680, ECO:0000269|PubMed:7846071, ECO:0000269|PubMed:8107847, ECO:0000305|PubMed:28524165}. This is the function of Ensembl gene identifier ENSG00000163914 (RHO, rhodopsin).