Editing Visual system (section)

====Photochemistry====
{{Main|Visual cycle}}
The functioning of a [[camera]] is often compared with the workings of the eye, mostly since both focus light from external objects in the [[field of view]] onto a light-sensitive medium. In the case of the camera, this medium is film or an electronic sensor; in the case of the eye, it is an array of visual receptors. With this simple geometrical similarity, based on the laws of optics, the eye functions as  a [[transducer]], as does a [[Charge-coupled device|CCD camera]].

In the visual system, '''retinal''', technically called ''[[retinene]]''<sub>1</sub> or "retinaldehyde", is a light-sensitive molecule found in the rods and cones of the [[retina]].  Retinal is the fundamental structure involved in the transduction of [[light]] into visual signals, i.e. nerve impulses in the ocular system of the [[central nervous system]].  In the presence of light, the retinal molecule changes configuration and as a result, a [[nerve impulse]] is generated.<ref name=Tov2008 /><!-- look up page from Tovée2008 -->