Picture This

 Picture This

    Imagine that you are sitting in a darkened room that has a tiny round window, barely the size of a quarter. The window allows some light to enter, perhaps from a moonlit forest, casting an image of trees on the wall opposite the window. This is the basic principle on which a camera operates.

    A camera consists of three main elements that are similar to the parts of a human eye. All cameras contain a device called a shutter. The shutter allows light to enter the camera, just as you use your eyelids to let in or shut out light. Oh some cameras, photographers control the amount of light by altering the length of time the shutter remains open.

    These cameras have a diaphragm, which also controls the amount of light entering the camera. The diaphragm is like the iris of your eye, which expands or contracts to limit the amount of light entering it.

    Light that enters a camera passes through a curved piece of glass or plastic that bends and focuses the light onto the film. This curved piece is called a lens, and unlike the lens of a human eye, it cannot alter its shape. In some cameras, the lens can be moved in and out to focus on an image on the film. The lens is moved inward to focus on distant objects and outward to focus on objects that are close.

    A camera lens causes rays of light to narrow and then create images on film. Because the light bends, the image is upside down. This is similar to the lens of a human eye, which registers an image upside down that is corrected by the brain. In a camera, the image is stored on film and is corrected when the film is developed.