4.11.1 Digital still cameras and camcorders

These devices are now widely and (fairly) cheaply available. There is no film. You point your camera, take your shot and get a compressed digital image that can be transferred straight onto a computer, where it can be edited or printed. Digital still cameras usually compress their images into JPEG format and store them on a tiny, removable memory card inside the camera; the latest digital camcorders can record in MPEG format, stored on a special tape. Both devices work by means of an electronic chip called a charge-coupled device (CCD).

A CCD is basically an array of tiny cells, vaguely similar to the receptors in the eye, that respond to light by generating a tiny electric charge. The amount of charge depends on the intensity and colour of the light falling on the cell. Each cell then maps onto a pixel in the image being stored, so the CCD behaves just like a bitmap. Obviously then, the larger your array, the higher the definition, and thus better quality, your image will be. The best non-professional digital still cameras now have CCD arrays of 5 million or more cells, giving superb-quality bitmapped images. Software inside the camera converts the bitmap into compressed format.