Stimulates two retinal guanylyl cyclases (GCs) GUCY2D and GUCY2F when free calcium ions concentration is low, and inhibits GUCY2D and GUCY2F when free calcium ions concentration is elevated (By similarity). This Ca(2+)-sensitive regulation of GCs is a key event in recovery of the dark state of rod photoreceptors following light exposure (By similarity). May be involved in cone photoreceptor response and recovery of response in bright light (By similarity). Subcellular location is not affected by light or dark conditions. In the retina, it is expressed in cone and rod photoreceptor cells. The N-terminus is blocked. The disease is caused by variants affecting the gene represented in this entry. Binds three calcium ions.