Digital Cameras

Digital cameras are a fully electronic form of photography, which still function in the same basic way as conventional cameras. Light enters the camera through a lens and falls on a light sensitive medium behind the lens; the exposure of this medium is controlled by a combination of an aperture and shutter. The difference from traditional cameras is that in digital cameras the photographic film is replaced by a light-sensitive silicon chip known as a CCD (Charge Coupled Device).

These silicon chips contain many thousands or millions of light-sensitive elements, commonly referred to as pixels. When light falls on these individual pixels an electronic charge is generated. The more light, the larger the charge. This charge, or voltage, is then converted into digital data, which with the relevant computer software can be converted into a picture. Coating individual pixels with either blue, red or green filters creates the various colours within the picture.

Picture quality, or resolution, is related to the number of pixels contained on the CCD. The greater the number of pixels the better the potential quality of the final image. The number of pixels is either given as a total number, or as a factor of the horizontal and vertical figures, for example, 350,000 or 640x480. The simplest cameras have resolutions of 350,000 pixels, whilst the more advanced cameras have resolutions of over 2,000,000. In order to get photographic quality in prints of size 7x5in, a camera of at least 1.3 million pixels is needed.

When a picture is taken the digital information is stored within the camera. For most cameras the storage medium is a removable card, known commonly as a memory card. There are a number of different types, each with varying capacities for holding information, ranging from 2-270Mb. The larger the memory the greater the number of images you can take before the memory card is full. The stored digital information can be downloaded into a laptop or desktop computer, and the picture can be viewed and printed as a final photograph.