Definition: Organ of vision on which all life, as photographers and other imaging artists know it, depends. * It is a roughly spherical body about 24mm in diameter consisting of a cornea or lens in front; a sclera, or external fibrous coat; a vascular layer consisting of iris or pupil of eye, ciliary body controlling shape of cornea and the choroid a layer providing for inner retina that contains the light-sensitive cells. * The eye is contained in the eye socket of the skull, moved by set of six extraocular muscles and protected by both skull and eyelids. * Focal length of normal human eye is about 16mm. * The pupil has a normal working range of rapid adjustment of about D/4 to D/8 but it can cover a wider range of D/1.8 to D/12 allowing more time for adjustment. * Entrance pupil - i.e. the pupil as one sees it - appears about 13% larger than it actually is, due to the magnifying effect of the cornea.
Related Terms: cones
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