Date: 10-16-07 04:08
In describing exactly how the human eye and man-made camera do, parallel to each other, one writer provided an interesting comparison of the two:
A camera works somewhat like the human eye ... But even they are no more than clumsy copies of the human eye ...
The human eye has an eyelid that opens to let in the light and closes to keep it out. A camera’s eyelid is a shutter...
The camera also has an iris. It is a circle of overlapping metal plates around a hole in the center. These plates shift when you set the camera for sunny or cloudy scenes. The hole in the center shrinks to cope with vivid sunshine and opens wider for dimly lighted scenes ...
The eye has a lens, just behind the pupil. It is a small saucer of glassy material with delicate muscles to pull it out thin or push it together and make it thicker. The changing shape of the eye lens brings near objects and distant objects into focus. The camera too has a lens. It is a magnifying glass, that cannot be made thicker or thinner. But fixtures inside the camera can move it back and forth to focus on objects near and far...
The camera’s retina is a piece of film in a miniature dark room behind the lens (Salt Lake Tribune).
Yet, the eye is infinitely more complex than any man-made camera.
* It can handle 1.5 million simultaneous messages, and gathers 80% of all the knowledge absorbed by the brain.
* The eye is self-cleaning. Lacrimal glands produce secretions (e.g., tears) to flush away dust and other foreign materials. Eyelids act as windshield washers. The blinking process (3-6 times a minute) keeps the sensitive cornea moist and clean.
* Tears contain a potent microbe-killer (lysozyme) which guards the eyes against bacterial infection.
* During times of stress, one eye will “rest” while the other does 90% of the work; then the process is reversed, allowing both eyes equal amounts of rest.
* The brain receives millions of simultaneous reports from the eyes. When its designated wavelength of light is present, each rod or cone triggers an electrical response to the brain, which then absorbs a composite set of yes-or-no messages from all the rods and cones. It sorts and organizes them, and presents the proper image accordingly.