Light-sensitive, photo-chemical material (film) is chemically altered when exposed to light and subsequently processed into a finished print using additional processing stages.

The charge of a light-sensitive, electronic sensor is altered when exposed to light, with the sensor producing a finished image through variations in these charges. The optical conditions remain basically unchanged. Both analogue and digital photography continue to use an optical exposure system to take photographs, except that the sensor is different (chip).

The term “pixel” is an abbreviation of picture element (or picture point). Pixels are square image points which combine to create a digital image. Each pixel on a digital photo corresponds to a photo diode on the chip sensor of a digital camera.

In principle the light-sensitive crystals of conventional film material are no different to pixels, just like the light-sensitive cells in the human eye.

The number of pixels first describes the size of the resulting image and is only secondly related to the aspect ratio.

Example: 1524 x 1012 pixels ~ 1.5 million. Aspect ratio ~ 3:2

Method used for neutralising colour casts when digital photographs are taken, which can occur when the colour temperature of the lighting conditions is not adjusted.

Most digital cameras have an automatic white balance feature. The colour composition of the ambient light is analysed by the exposure sensor and assigned to a colour temperature range.

The image resolution of the CCD chip has the greatest influence on how sharp and detailed the images are.

It is determined by the number of CCD elements (photo diodes) on the surface sensor, either as a total number or as a proportion of width and height. This has to be differentiated from the resolution with which an image can be reproduced either in printed form or on the monitor without loss of quality.

The pixel dimensions also directly determine the output size, i.e. the maximum size with which an image can be reproduced before the eye is irritated by its ability to perceive the pixel structures.

Colour depth is expressed as the number of possible tone shades per colour. A camera with an 8-bit colour depth digitises 256 different shades per colour channel (red, green and blue).

In a three-channel image, this results in around 16.7 million possible different colours.

Image storage devices are either built-in or removable devices used for storing digital or analogue image information.

No one standard has yet established itself for digital image storage devices. They vary from one manufacturer to the next and also in storage capacity. Examples include Memory Sticks, Memory Cards and Smart Media Cards.

Compression methods in a digital camera do not reduce the number of pixels; they reduce the amount of space required to store an image, at the expense of a slight loss of quality. The camera software analyses the image taken to see whether certain colour information is dispensable and alters the colours accordingly. The aim is to reduce the number of different colours in the image in such a way that the overall impression created by the colours does not suffer.

Quality losses include loss of sharpness, a coarser image or reduced contrast.

There are two types of scanners: transmitted light scanners for transparent film material, and incident light scanners for images. They are used for digitising analogue image storage media (films, slides, pictures, prints).

(Digital) cameras usually contain a CCD chip on which the image (light) data is perceived as electric charges and subsequently processed with the aid of the camera’s software.

The key characteristics of digital camera systems include: