What is colour temperature?
Colour temperature is important to the cinematographer for a number of reasons. Technically, it is vital that any light source that is to appear neutral in the final rendition of the scene is emitting light of the same colour balance as that for which the film has been designed. Artistically, it is important that the cinematographer has an understanding of the psychological and emotional effects of the colour of light within a scene and that they have complete control over this colour.
In order to evaluate and control anything, we must have a unit of measurement and a means of measuring. We measure differences in colour temperature in degrees Kelvin (°K) using a colour temperature meter.