Barbara Giles age 10, of Milwaukee, for his her question:
Is it true that the camera is like an eye?
It is true that the camera is a rather clumsy copy of the human eye. Even the finest camera is merely a machine, whereas the eye is a small living miracle. Yet the operating parts of both true eye and the camera are very much alike.
The eye has an eyelid which can be opened or closed to let in the light or keep it out. The camera's eyelid is a shutter. An image of the scenery enters the camera when we click the shutter open.
The colored part of the eye is called the iris. Actually, it is a delicate muscle surrounding a small black hole, which is called the pupil, Light streams into the sensitive inside of the eye through the pupil. When the light is very strong the iris contracts, making the pupil smaller so that less light can enter. When the light is dim, the iris relaxes making the pupil larger to catch every glimmer.
The camera too has an iris. It is a small ring of overlapping metal plates folded together to leave a hole in. the center, These plates move when you set the camera for cloudy or bright scenery. As in the eye the hole in the middle shrinks to cope with bright light and expands to cope with dim light.
Just behind the pupil of the eye is the lens, which is rather like a small magnifying glass. It is held in place by a delicate muscle which can pull the lens out flat and thin or squeeze it short and thick. When you look at close objects, the little lens is flat and thick. When you look at distant objects, the lens is pulled flat and thin, The lens and its muscle working together bring the scenery, far or near, into sharp focus.
The camera too has a lens, which is a real magnifying glass. Since it is not made of tissue, like the lens of the eye, it cannot be made thicker and thinner. It is adjusted back and forth inside the camera. This operation as in the eye brings the scenery into sharp focus,
Lights bearing an image of the object passes through the pupil and the lens and falls upon a screen on the inside back wall of the eye. This screen is the sensitive retina which has about a million tiny nerve cells. These cells sort out the picture into patches of colors light and darks and flash the information to the brain,
The cameras retina is a piece of film on the inside back wall of the box. The surface of the film contains countless millions of silver bromide molecules. Light strikes the film with patches of bright and dim. This causes a chemical change in the silver bromide. When the film is properly developed and printed we get a camera copy of the picture which came through the iris and the lens.