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factfile3.8 How cameras work


A camera is an image capture device. From the simplest pinhole camera to the most complex technology the principle of how cameras operate is the same, consisting of three basic elements: optics (lens/pinhole), a lightproof container (camera body/ darkened room) and a recording support (film/electronic sensor/wall).


Rays of light from an object are redirected through the lens so that they converge back to one point, forming the image, but because light travels in straight lines the projected image is reversed and upside down.

The word 'camera' comes from the Greek word for room; while 'photography' literally means 'drawing (graph) with light (photo)'. Sir John Herschel, a 19th century astronomer and one of the first photographers, invented the term in 1839. In daylight a chink in the blinds or curtains of a darkened room will allow an image of the scene outside the window to be projected onto the wall opposite.

Visitors to the surviving Victorian Camera Obscura (literally 'dark room') attractions in Edinburgh or Bristol can still see this effect clearly. Photography was made possible when someone discovered a chemical method of recording the reflected image or "light drawing" permanently.

One of the most influential technological breakthroughs of the past two decades has been the way in which visual and audio data is handled: conventional analogue information (represented by a fluctuating wave) is converted into digital data (represented by ones and zeros, or bits). Whereas conventional cameras depend on chemical and mechanical processes, digital cameras have a built-in computer and record images electronically by focusing the light that passes through the lens onto a sensor or CCD, rather than film.

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