Visual pigments are the light-absorbing molecules that mediate vision. They consist of an apoprotein, opsin, covalently linked to cis-retinal. Retinal double cone principal photoreceptor cell outer segments. First detected in the retina at 51 hours post fertilization (hpf) along the nasal edge of the choroid fissure. By 55 hpf expression has extended into the nasal region and by 72 hpf it covers the whole retina. Phosphorylated on some or all of the serine and threonine residues present in the C-terminal region. Belongs to the G-protein coupled receptor 1 family. Opsin subfamily.