The human eye is often compared with a camera. Both share similar functions, according to Kellogg Eye Center at the University of Michigan. Although many of the parts of the eye and camera are comparable, certain aspects of the mechanisms of each operate differently.
The camera and the human eye both process light and record images. A camera uses light to capture images on film or on a computer chip or memory card, but the eyes process light and send image signals to the brain. The sensory perception of sight is achieved inside the brain, not in the eyes.
The outer covering of the eye is called the cornea, which is compared to a camera's lens cover, but it is different in that the cornea does more than cover; it actually converges light, bending the rays into the eye. A lens cover on a camera simply keeps the camera closed and prohibits light from entering the camera. The University of Georgia's HyperPhysics Department notes that about 80 percent of refraction, the phenomenon that makes image formation possible in eyes and cameras, occurs in the cornea 1.
Cameras have an aperture, a hole through which light passes to the inside of the camera. In the eye, the aperture is the pupil. When a person blinks or closes his eyes, light is not able to go through the pupil and enter the eye. A camera has a shutter that opens and closes to allow or shut out light.
Both a camera and a human eye have lenses. There are two main differences between a camera lens and a human lens, also called the crystalline lens. The lens of a camera sits in the very front of the camera and is visible; a human lens is inside the eye. The other difference is focus ability. A camera lens is adjusted by the photographer to bring an object into focus, but the human lens has its own focusing mechanism called the ciliary muscles. The University of Alabama notes that these muscles change the shape of the crystalline lens when the eye views objects at different distances and adjusts the lens 1.
The back of the eye, called the retina, is like the film or imaging area of a camera. According to the American Optometric Association, the retina is a thin layer of tissue at the back of the eye that contains millions of tiny light-sensing nerve cells called rods and cones. The retina changes the light into electrical impulses and sends them to the brain through the optic nerve. The image is perceived in the brain so a person actually sees with his brain, not his eye. Comparably, a camera "sees" with film, or a memory card.
- photographer with camera at shooting moment image by Oleg Mitiukhin from Fotolia.com