Can you spot the snipers hidden in these photos?

About half of them, my eye landed on them first thing. They were ridiculously easy. I couldn't tell you why the spot was wrong, just that it was. The other half, I couldn't find if my life depended on it, as I suppose it would if I got mixed up in anything that involved snipers lying in wait.

I have no idea if I got the half I did because I'm observant or because I'm a mutant. Possibly both. My mother's father ended up fixing radios and jeeps for the Army Air Corps instead of flying planes because he was deuteranopic, commonly known as 'red-green colorblind'. I'm told that the infantry informally used colorblind soldiers to spot stuff stashed in jungles and woods; I don't know if they still do, or if that would even work in a rocky beige desert. Turns out that when your brain isn't distracted by all those greens, cammo net stands out like a sore thumb.

About 1% of all men are red-green colorblind. The relevant gene is carried on the X chromosome. Colorblind women are rare; you'd have to be unlucky enough to inherit two copies of the same mangled gene in order to get no properly working medium-wavelength cones. Female carriers with male relatives who are colorblind are much more common.

It's possible for a female carrier of the gene to have the normal dominant copy expressed in some of her cells, and the mutated recessive copy in others, via a process called X-inactivation. This would give her four kinds of cones -- short, medium, long, and weirdo -- and make her a tetrachromat, potentially better able to discriminate between colors on the visible part of the spectrum. I score only middling-well on tetrachromacy tests, although a lot of places, like this one, say that it's not possible to use a red-green-blue display to test for red-green-blue-octarine vision.

On a practical basis, I'm one of those people who insists there are different shades of "black" and "white". Everyone asks me when they want to know if two colors are the same or not. I don't bother taking swatches along when I go to buy sewing supplies, because I can color match to the eidetic snapshot in my head.

The last item on that FAQ is particularly interesting to me. I never thought to ask about it, although I doubt it would have done me much good if I had -- it took me ten years to get anyone to stop laughing long enough answer me when I asked if people who didn't wear corrective lenses also saw fuzzy halos around streetlights at night. The color vision is faintly but noticeably redder in my right eye than my left. Been that way forever. As a kid, I wondered if it affected what color cellophane went over what eye when you wore 3D glasses, but I never got around to investigating.

Barring some sort of bizarre neurological disorder that somehow only hit one kind of cone on one eye and never affected any other part of me in any way ever, I'm pretty sure the only way you could get a different white balance on each eye would be to have a bunch of weird cones in one of them. So congratulations, me! I probably qualify as a tetrachromat. Studies show a prevalence of 2-50%, so the rarity is somewhere between "natural redhead" and "below-average height".

I'm pretty sure I'm also getting something just off the UV end of the spectrum. I'm not magic; the human retina is sensitive to UV light, but the cornea and vitreous humor (i.e., the lens and your eyeball goo) filter most of it out. Cataract patients who have had their natural lenses removed and not yet had artificial ones installed report gaining superpowers changes in their vision, mainly that some things now seem a very bright bluish-purplish-white. Since whites only bloom like that for me in absolutely blazing sunlight or during a migraine aura - two things which are sometimes unfortunately related -- I'm guessing what's happening is that the lens and humor actually only block 99% of the UV coming in, and my brain just ratchets the signal way up when it feels like being a dick, noise floor be damned.

Or I could just be paying way the hell too much attention to something everyone sees and normally ignores. That also happens.

Still, the stuff that blooms when I'm about to get a killer headache is the same stuff that glows under a blacklight, and it blooms in a fiercely exaggerated version of what I used to contend with in Arizona in the summer. The photo of the gym shorts, where he points out that they have a purplish cast under UV, I also find telling. I used to stock clothing at a department store, and I was forever having to fix racks full of things just like those gym shorts, because whoever tidied up before me had just jammed all the different blacks onto one arm of the stand and walked off. I wonder now if perhaps they genuinely could not tell the two colors apart.

[ETA: Missed it the first time I skimmed, but cataract surgery dude also mentions a bluish haze on pavement. Christ, yes -- Arizona is paved everywhere, not that the surface is much different than the proto-sandstone that passes for dirt in those parts. Summer was miserable; there was nowhere to escape from the glare. When I later moved to a place wot had actual seasons, I discovered that snowbanks can be just as bad. And, during auras, white linoleum tile under fluorescent lights. I definitely do not see as vividly as he does, though. I could probably have used one of Moggie's portable blacklights as a flashlight in a dire emergency, but I don't know what wavelength they were and inasmuch as it was a small lamp and probably very cheap, I don't know how much light it leaked in the normal visible spectrum. They were not anywhere near as bright as his example.]


  1. As someone who both cannot see different blacks and stocks clothes for a living (for, I believe, the same company for which you used to work, actually), I would just like to say that my job would be so much easier if I could tell those wretched gym shorts apart more easily than by peering at the seaming.

    Also I couldn't see the snipers, but, interestingly, in several of the pictures my eye went right to the place where they were supposedly hiding. Couldn't consciously find them, but apparently I picked up on something off anyway.

    1. I half wonder if it has something to do with my contacts. The graph on cataract surgery dude's page indicates that younger people see more into the UV part of the spectrum -- it eventually fades out as your corneas harden and yellow over time. I don't know what causes the transformation and I can't find anything online that would tell me. I've basically been wearing squidgy plastic lens caps over my eyes almost 24/7 for the past twenty years -- and I had some of the first continuous-wear hydrogel soft contacts, way back when, so I'm about the oldest person you'll find who's been able to do that. If the yellowing is at least partially to do with eternal factors, I may have just accidentally preserved my eyeballs in plastic.

  2. I am super curious how you score on .

    1. which I now realize looks super spammy. It's a hue-discrimination test.

    2. Not as hilariously well as you'd think from watching me in real life. One, as mentioned above, you can't really use an RGB display to test for RGBX vision. The way they run the color matching test for tetrachromats in person is that they show them a mix of colored lights, then tell them to recreate the mix with lights of their own. Tetrachromats will get the original mix, or close to it. Trichromats will find multiple different mixes that, to them, look exactly like the original. I've never had an opportunity to take one of those. I expect to get funny looks if I do, same as I get from all the other psych and perception people.

      Two, as mentioned elsewhere a few times, my monitors are all adjusted funny. I keep them set well to the blue of PAL color. It drives other people bonkers on occasion, but if I don't, the whites register as dingy. So no color test is going to come out as the makers intended unless I crank the monitor color temp down to the point where it gives me kind of a headache.


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