Dark adaptation

Patent Pending Rhodopsin, a biological pigment in the photoreceptors of the retina immediately photobleaches in response to light.[4] Rods are more sensitive to light and so take longer to fully adapt to the change in light. Rods, whose photopigments regenerate more slowly, do not reach their maximum sensitivity for about half an hour.[1][5] Cones take approximately 9–10 minutes to adapt to the dark.[1] Sensitivity to light is modulated by changes in intracellular calcium ions and cyclic guanosine monophosphate.