An often-overlooked aspect of light is its colour – it is something that photographers can underestimate. When someone talks about bad light, or muddy light, or indeed nice light or beautiful light, they usually mean both the quality of the light and the colour of the light – or more specifically, the colours (plural) of the lights (plural). Different sources of light (even though nominally white) have different colours. Often those colours don’t play well together. If they don’t, we can perceive it as bad light.
A flourescent bulb, for example, casts a green colour, while a cloudy day casts a blue colour, and a tungsten bulb casts an orange colour. Your flash is balanced to match the colour of the midday sun, which is warmer than a cloudy day but cooler than a sunrise. And if you only take one thing away from this whole blog, I’d be delighted if it was to understand the impact of the colour of light on photographs – both ambient light and added light – and how to make that work for you rather than against you.
Colour will be a focus in lots of photos we discuss. The reason it’s so important for low light photography especially, is because when we deal with darker exposures, generally colours get more saturated. And if the colours don’t work well together, very quickly you find yourself cursing “horrible light”.
For light, colour is measured as a temperature in units of Kelvin. We don’t need to know the actual values, just how they interact. Midday sun is typically the reference point, and is about 5,500 Kelvin, and that’s what a hot shoe flash or a studio light is typically calibrated to.
Don’t worry about the actual values for different light sources. All you need to know is the relative colours of different light sources in the scene, how to mix and match them, how to correct them, and how to put them to creative uses. When I break down a photograph, I’ll always talk about colour.