Location Lighting for Television

6

Colour Temperature/ND Filters

6.1   Colour Temperature – Defining White

Defining what we mean by ‘white’ is a major concern in colour television. The process of calibrating the colour camera ‘white’ point is known as white balance, in which the camera is exposed to a line-up chart or white card suitably lit with ‘white’ light. The camera’s autowhite balance facility equalises the RGB signals (R and B matched to G) so that the line-up chart or white card looks neutral or white.

Our perception process accepts many sources of light as white, e.g. daylight, tungsten light, fluorescent light, metal halide discharge lights, xenon lights etc. So how can we define what is meant by white? One convenient way is to use the concept of colour temperature ...