Colour - the Science behind the sense - Ben Craven

This week we had another fascinating lecture by Ben Craven, this time on colour and how we see it. He started off by pointing out that we are all in fact colour blind! There is actually no objective reality to colour - animals and humans all see colour in a different way, and none of them are the "correct" view of the world.

So how are we colour blind? Our eyes use three types of colour detecting cells. They each detect light from a different area of the spectrum, each giving the strongest signal for their particular area. The brain then compares results from all the cell types to work out what colour something is.

This also means that we can easily be tricked. Look at the image below:

It shows a red pen in a box. The box is split on to two compartments, each with apparently identical lights. But the lights are not actually the same. One is from a yellow light; the other is a mixture of red and green, which we see as yellow. As a result, the pen looks different under these two different - but apparently identical - lights. Under the red/green light, the pen looks red, as there is red light to reflect off it. Under the purely yellow light, there is no red to reflect off the pen, so it looks grey and dark.

 Ben demonstrated this principle to great effect with a red pepper during the demonstration. Under one light the pepper looked unbelievably vivid - both the red fruit and the green stalk. But under the other light, the pepper actually looked black!

All of this was a fascinating and important insight in to how we see colour and how important the light is to what we see.