Let there be light
Look carefully, what colour is that light? Isaac Newton taught us that light is not white, but instead made up of a spectrum of seven different colours. Red, orange, yellow, green, blue, indigo, and violet. Interestingly, he only chose seven because he suspected a natural correlation between light, music and time (the 7 days of the week).
Two hundred years later, the seven colours were reduced to three when scientists learned that we have 3 types of light receptors in our eyes, each sensitive to a different range of visible light: red, blue, or green. RGB. And mixing those three colours creates the hues that we see. However, we do not see all three colours equally well. For example, fewer receptors are sensitive to blue, more are sensitive to red but most are sensitive to green and yellow. Our brains compensate for the blue light at midday and the warm evening and morning light, so that we hardly notice the colour of light changing through the day as the sun crosses the sky.
In photography and video, modern digital cameras use the same RGB principle - and AWB takes care of the changing light (Automatic White Balance) which can also be adjusted later in post-production. But when blue midday light is coming through a window into a room filled with warm electric light the result is unnatural and unattractive.
The colour of light is measured in the Kelvin temperature scale and to balance the light in film and photography, it’s temperature must be taken into account: and coloured filters and gels are often necessary to solve the problem of unmatched light sources.
The temperature of light
So even if cameras will do most of the work for you, understanding the colour of light is still fundamental to film-making and photography - and there is still a need to take colour temperature into account, and thus for skilled camaramen. Quite reassuring really.
David (Nick) Newton Dunn - January 2013