It’s not possible to compensate for every single light source, and sometimes the colour of the light doesn’t fall neatly on the warm-cool colour temperature scale. White balance adjustments work by shifting the whole spectrum of the light source up or down the scale. They rely on the light having a full spectrum of colours, but simply shifted one way or the other.

Some light sources don’t have a full spectrum of colours. The prime example is orange streetlamps. They look orange because that’s all there is – no blue, no green. It’s impossible to correct orange streetlighting to produce a full range of colours.

Fluorescent lighting is the other oddity because it contains excess green. Digital cameras deal with this with one or more dedicated ‘fluorescent’ settings. These increase the levels of magenta (green’s complementary colour) to restore a naturallooking colour balance.