Colour information is not faithfully maintained by a CCTV imaging chain. Since colour can play an important role in
identifying objects it is beneficial to be able to account accurately for changes to colour introduced by components in the
chain. With this information it will be possible for law enforcement agencies and others to work back along the imaging
chain to extract accurate colour information from CCTV recordings.
A typical CCTV system has an imaging chain that may consist of scene, camera, compression, recording media and
display. The response of each of these stages to colour scene information was characterised by measuring its response to
a known input. The main variables that affect colour within a scene are illumination and the colour, orientation and
texture of objects. The effects of illumination on the appearance of colour of a variety of test targets were tested using
laboratory-based lighting, street lighting, car headlights and artificial daylight. A range of typical cameras used in CCTV
applications, common compression schemes and representative displays were also characterised.