Human eyes have often been compared to cameras. They are alike in terms of structure, but they have one fundamental difference in functioning mechanism.

Table: Similarities & the Difference between Camera and Human Eye

	Function	Camera	Human Eye
Similarities
1.	opening for light to enter	aperture	pupil
2.	control the amount of light entering camera/eye	diaphragm control size of aperture	iris muscles control size of pupil
3.	refract light	glass biconvex lens	mainly cornea ; lens, aqueous & vitreous humor
4.	object of light action to form image	photosensitive chemicals on film	photoreceptors(rods & cones) in retina
5.	absorb excessive light to prevent multiple images formation	dark internal surface	pigmented, dark choroid
Difference
1.	focusing mechanism	change distance between lens & film	change focal length of lens using ciliary muscles