Color Perception Explained – Sort of

In my last post/presentation on autism I included an example of how all people are inherently different perceptually. The example I chose was the famous “Is my red, your red?” color perception study from Vsauce…but it turned out to be perhaps a poor choice as then I still got questions from teachers, students, and one psychologist about how we perceived colors differently.

So to clarify that a bit, here is an explanation of color perception – sort of.

Color perception is both a legitimate field of science and one of the oldest of the original forms of speculation.

The question “Is my red your red?” is thousands of years old and has been traced back in lore to Asclepius, the first physician.

The conflict has two parts, the original philosophical/metaphysical and the purely physiological.

The first runs something like this, how do I know that when I look at the sky the color I see – which I call blue – is the same color you see – which you call blue? How do I know that your sky is not what I would call green?

The idea here is that red, blue and green are color labels, that is to say that they are words…and we all know that word labels change from culture to culture and language to language – vidlička, چنگال ,

çatal, شوكة , tenedor, forchetta ,haarukka, and Πηρούνι all mean a three tined implement or tool, and even in English there are varients on what a fork is – salad fork, pitchfork and garden fork.

So if blue is just a label than how do I know that you see what I see? It is quite probable that you see what I would call green but your mother, your teacher, your doctor all call that color blue so so do you.

But what about the physical properties of light, you ask. That does not change, right?

No it does not.

BUT how you perceive it does.

This is where the physiology comes in.

The segment of your eyes that senses light waves and deals with color vision is duly labeled as the retina in our language and within the retina there are structures that are shaped like, and thus imaginatively called – rods and cones.

Rods help to see in low light, cones help to see in color and also with seeing details. Rods and cones contain photosensitive chemicals. In rods, this chemical is named rhodopsin. The chemicals in cones are called photopigments.

Now to get dully technical, there are three kinds of cones, and each cone has a different photopigment that’s sensitive to a certain wavelength of light. Because most of us have all three kinds of cones, normal human vision is called trichromatic.

As Oliver Sacks points out in Island of the Colorblind colorblindness is a (another) misleading term. It makes it sound like the colorblind see in black and white like in early Hammer films or Noir movies about guys with big guns and ladies in small dresses. “Color vision deficiency” might describe the conditions more succinctly and with greater accuracy.

And there are three different kinds of color blindness, depending on which cones are defective, with red-green color vision defects being the most likely. For you name people, a defect in red perception is deuteranomaly , green defects are protanomaly, and Tritanomaly, the rarest form constitutes issues with blue and yellow.

But this is just the most striking example, if you have a computer or a smart phone than you deal with another case where your color perceptions are skewed, rather deliberately, and in this case by tricking your brain.

To use the famous “This is not yellow” example (Vsauce/Youtube), when you are in the room with a lemon you see a yellow lemon.

Someone watching that room on a computer screen also sees a yellow lemon.

BUT is it not the same kind of yellow. The actual lemon in the room is subtractively yellow (true yellow). The lemon absorbs all the visual wave lengths of light except for those that equal yellow and then reflects that wavelength onto your eyes and thus your retina. The cones in your eyes are RGB, red, green, blue. Remember that. So what happens next is that the since yellow is a mix of red and green those cones are both slightly activated and your brain translates this as whatever you perceive as yellow.

What you see on a computer screen, which is also RGB, is not even vaguely real yellow. It’s blend yellow. Computer pixels are strictly RGB, they do not blend. So the lemon on your screen is really made up of thousands of very very small red and green pixels and the mix of red and green light that hits your retinas is calculated to be the right frequency of light to activate the same cones, red and green, in your eyes that makes yellow. Your brain then blends these colors and tells you you are seeing yellow.

So again how could this tell me if my blue sky be different from your blue sky?

Well, scientists at the University of Rochester who were working with RGB scalings discovered sometimes the RGB computer trick did not work properly, and that the people it did not quite work for were not actually medically colorblind, so from there they went on to discover that no two human retinas are the same shape nor do they contain the same number of cones and rods.

Each eye is as different as any camera lens and studies had already proven that light through any two camera lens was perceived differently by the cameras’ “retina” – it’s CMOS sensor in digital camera or the film in SLRs. The tiniest imperfection, chip, bulge or concavity changed the color of the finished image.

Digital artists know this to their chagrin as do most photographers. The same image looks different on different screens with different perceptive and emotional effects.

So Dr. David Williams and his research team, led by postdoctoral student Heidi Hofer, now an assistant professor at the University of Houston, used a laser-based system developed by Williams that maps out the topography of the inner eye in exquisite detail. They then made computer models of those eyes and shown light through them.

The result was about what they had expected. No two people actually saw blue the same way. So on a physiological level, my blue is not your blue.

Where it got weird was that when they then asked participants to point to yellow, they all got the same basic answers. Lemons are yellow. So they hypothesized that one of two things were going on, that a) there is a serious linguistic hangup because we were all taught that grass is green and lemons are yellow or b) that the brain has an auto correct feature somewhere that we have not found yet that makes us all translate the very different things our eyes are actually seeing into some kind of mental consensus.

So in short, as of this moment we can not be really 100% certain that my yellow is your yellow on a fundamental level, but we can say that what I see is yellow is not what you see as yellow…which may explain why my boyfriend really does think that his seventies plaid pants go with his seventies plaid shirt even though the combination makes me want to rinse my eyeballs with bleach.

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