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A traditional camera, from a camera obscura to the latest digital wonder-cam, is essentially a light-tight box. A hole (aperture) is made at one end to admitlight, and some light-sensitive material (usually film or a digital sensor) is placed inside the box opposite the hole. The camera’s purpose is to enable the light to form an image on the film. This can be accomplished a variety of ways, but most modern cameras have the same basic components. These include the following:

• A viewing system that allows accurate composition of the image.
• A lens, instead of a hole, that focuses the rays of light to form a sharp image at the back of the camera. This image is upside down and backward. The lens also determines the field of view and influences the depth of field of the scene.
• An adjustable diaphragm, usually an overlapping circle of metal leaves, that creates an adjustable hole called an aperture. The aperture control the intensity of the light that passes through the lens. When it is widened (opened), it permits more light to pass through the lens. When it is closed (stopped down), it reduces the amount of light passing through the lens.
• A shutter mechanism that prevents light from reaching the film until the shutter is released. The shutter opens for a measured amount of time, allowing the light to strike the film. When the time has elapsed, the shutter closes, preventing any additional light from reaching the film.
• A focusing control, which changes the lens-to-film distance, thus allowing a sharp image of the subject to be formed at various distances.
• Light-sensitive material, traditionally film though now often a digital sensor, that records the image created by the light. Most cameras use roll film, cassettes, or individual sheets. The latest digital camera record images magnetically on memory cards, optical disc, or tape.
• A holder for the light-sensitive material. This is a system or device designed to maintain the correct position of the film in relationship to the lens.
• A film advance mechanism, in roll or cassette cameras, that advances the film after an exposure is made to the next unexposed portion of the roll or cassette. Most modern 35mm camera have some sort of automatic advance, some at a hight rate of speed. Sheet film is loaded into film holders that are put in the back of the camera. Electronic imaging cameras automatically go to the next free space on the storage medium.
• A light meter, usually built into the body of the camera, measures the intensity of the light.