How you see color, part 3

So if light is just a wave of energy, how do we see color? How do we see at all?




You eyeball has specialized cells called cone cells. Cones come in three different types. Each type is sensitive to a different wavelength on the spectrum. The cones are usually referred to as short, medium, and long, often shortened to S, M, and L, for the length of the electromagnetic waves they sense.



You might think that the three types of cones must see red, blue, and yellow, the three primary colors. However, these colors don't really correspond nicely to colors. L cones, for instance, are sometimes referred to as red receptors. Actually, they are closer to green-tinged yellow. The other cones, likewise, do not easily match up with primary or secondary colors. As a matter of fact, cones' light perception varies from person to person. The different cones' are sensitive to overlapping ranges of light, which is what lets us sense the variations.



The genes for sensing visible light are carried on the X chromosome. That is why color blindness is more common in men, and why some women have an extra type of cone, which can allow them to see light beyond what is visible for most people.



In lower lights, different cells, called rods, sense light. Rods don't have much to do with color differentiation though.



Intensity and amount of light is what determines the saturation of color. Saturation describes how dark or pale a color is.



Once the cones – and to some extent, rods – have absorbed the light, the nerves send that information to the brain, which puts the information together to form the images that you see. Interestingly, the inside of the eye sees the image in front of you upside down, and the brain has to flip it back right-side up in order to be useful to you in navigating the world.