Seeing in color

This is how my husband sees my work. That's because he's a dichromat; he only perceives two spectral colors, green and blue. People with normal color vision are trichromats. They perceive the world in three colors, red, blue and green.

Colorblindness is sex-linked, so most people affected are male. Colorblind men inherit the trait from their mother, an unaffected carrier. The men themselves have sons with normal vision, and daughters who are carriers. Since we did not have any daughters - just two trichromate sons - the trait will be lost with Alan. And it also means that Alan lives in a house where everyone sees in full color but him.

Alan is pretty used to the fact that people ask a lot of questions when about his vision. And since he is, by profession, and optical physicist, he's probably in a better position to explain just what being colorblind means. But even so, it's really hard to explain to someone what it's like not to see red if you really have no concept of red in the first place. Now in his forties, I think Alan has given up trying. Unfortunately for him, his seven year old son is just starting to ask. And he is the ultimate, "Hey, Dad, I have a question" kind of kid.

After another round of frustration on all sides, I decided that surely the internet must have some kind of side by side comparison that shows what images look like when you are colorblind. Alan will, of course, never see our version, but we could see his. With all that computers can do to tweak images, someone must have done this. And someone had done that here. I even found a site with something called the Dalton Algorithm, which could convert any image into the various types of colorblindness. That's how I got my adjusted image of my foxtrotter medallion.



Here my medallion is in his unadjusted form. I was surprised by these images, maybe because the term most people use for this kind of colorblindness is "red-green colorblind". I assumed that meant Alan saw neither red nor green. I envisioned a world that looked somewhat like one of those old sepia photographs with some additional blue tones, since I knew that he could see blue. What I didn't realize was that he can see green. In fact, his world is pretty much all green, because he sees red as green. That would explain why it's so hard for him to tell when meat is cooked through. (For a good look at that, see the third slide in this presentation.)

But even more interesting, and the reason I thought I would share all this seemingly unrelated information, was a note on one of the colorblindness sites about tetrachromats.

Where people with normal color vision are trichromats, some animals are tetrachromats. They see the world in four colors. What I didn't know was that there was a theory that some people (women, actually, since color vision is sex-linked) see in four colors. In theory, this trait would result in women with extremely sensitive color vision. They would see subtle differences in color that were lost on other people. In one article I read, women identified as potential tetrachomats could see tints in colors others could not, so they often had the sense that things did not match properly. They also were said to be able to carry a color image in their head more easily, and, for example, match a dress to a pair of shoes even though the dress was not there to compare. As I was reading these things, I kept thinking that they weren't describing some rare genetic mutation. All that were talking about was someone with artistic leanings. That's just what artists do! Aren't we all good at those hue tests?

But the more I thought about this, the more I wondered if I have been mistaken all these years. I've always known that I was very sensitive to subtle shifts in color. Friends and family have commented on it all my life. I just thought it was inclination and exposure. I figured if someone spent enough days mixing and matching paint, they would end up just as sensitive to it. It never occured to me that I might be seeing a distinction that others literally could not see. What if, when talking about how to identify some of the dilution genes in horses by the difference in their tone, I was suggesting someone look for something they could not see? Or that my tip about using Photoshop for color mixing might be more than a time-saving shortcut for someone? I don't know if I really do see in four colors, but reading up on color vision (and lack of it) has made me think in new ways about how I talk to others about color.

[Oh, and just a fun aside... the hue test I linked to is hosted by a company that makes scanners that identify colors. If you've ever had a paint chip analyzed at a home improvement store to get a matching bucket of paint, you've probably seen one. My husband worked on the team that developed some of the science behind those scanners. But he couldn't pass that test if his life depended on it.]