Friday, October 29, 2010

Color Blindness Myths and Misunderstandings | Joe Dolson Accessible Web Design

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Color Blindness Myths and Misunderstandings

I’ve always believed that web site accessibility depends on an understanding of accessibility issues — not on technical issues. Obviously, knowing the technical side of web site construction and how it impacts accessibility is very important. Some decisions are fundamentally technical, but a huge part of web site accessibility is purely visible — and just understanding accessibility issues will make a huge difference.

To that end, here are a few quick comments about color blindness. Color blindness (or color perception deficiency) is an issue for approximately 1 in 12 people, mostly men. However, color perception problems are not always very effectively diagnosed, so these numbers could be low.

Color blindness is an inability to see certain colors.

Color blindness is really a misnomer. People with various types of color blindness are better described as being color vision deficient: it’s an inability to distinguish colors, not an inability to see color. People at the furthest limits of color deficiency, however, may have such an extreme inability to discern colors that this can be a fairly accurate description.

Individuals with color vision deficiencies can’t see red.

Well, no. Assuming we’re discussing Protanopic or Deuteranopic color blindness, in which the individual is missing either the red or green sensitive cones, the actual problem is that they may not be able to distinguish the color red. The color isn’t readily differentiated from other hues of the same shade or tint. Red perception deficiency is certainly the most common type of color vision deficiency, but it’s certainly not true of all individuals with poor color vision.

You have normal color vision

Not really. In fact, color perception is a spectrum for all of us. What’s commonly referred to as color blindness is actually only the portion of that spectrum which is considered anomalous — where the ability to perceive color begins to impinge on normal interactions with the world. Having “normal” color vision simply means that you don’t generally experience problems because of your color vision. You may well still fail an Ishihara test.

Color perception deficiencies are inconvenient, but don’t pose any serious problems

Particularly in our modern, technological society, color perception is a critical part of comprehending the world around you. From LED indicators which blink red, green, or yellow; to weather maps which a spectrum from red to green indicating storm severity; to knowing what color a traffic signal is showing if you’re in a location with a different signal orientation than what you’re familiar with. Outside of technology, color deficiencies can impact recognizing that you’re developing a severe sunburn or knowing whether you’ve actually cooked that hamburger enough to be safe.

People with Color Perception Deficiency have better Night Vision

Actually, I couldn’t definitely verify this one way or the other. There are a number of claims that this is true, but the reasoning is highly variable and not particularly evidence-based. It’s possible that certain types of color perception deficiency may give people better night vision, but it’s also possible that since some types of color perception deficiencies cause people to be photosensitive, those people may feel like their night vision is better, simply because it’s much better than what they’re accustomed to. Regardless, any evidence which is reasonably definitive would be appreciated.

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12 Comments to “Color Blindness Myths and Misunderstandings”

  1. Vivek R (new comment) says:

    I am color blind (fail 3 on the test) and my wife is not. We have frequent power outages at night and I am the first to find the lighter / candles. She’d have no clue they were where I picked them up from. I wear glasses too (shortsighted) but she has perfect vision. This is the first time I am reading about others who experience this.

  2. Loren Pechtel (new comment) says:

    I will definitely agree with color vision problems and camouflage, although my understanding is that the military has figured out how to make camouflage that works against those with color problems also. I have some red-green weakness and I think I was like 12 or 13 before I understood what camouflage was supposed to be — most every example of it I saw stood out like a sore thumb to me.

    Just because it blends in well for someone with normal color vision doesn’t mean it blends in with abnormal color vision.

  3. ColoUr Blind Pete (new comment) says:

    I’m colour blind, in the sense that i can’t tell the difference between brown, red and green. i can sometimes make correct intelligent (or so i think!) guesses. However I really do see better at night than my girlfriend for example. It’s little consolation for not fully enjoying the full spectrum of colour nature provides, but at least if i get stuck down a mine it might help!

  4. crazybat (1 comments.) says:

    Hey Joe!

    I must say that I’ve never heard about colour blindness and having better night vision. Interesting.

    It would also be interesting to see if there’s a correlation between the severity of colour blindness to more effective night vision. Get snopes on the case :)

    I personally fail in only one circle on the Ishihara test (the 6). I do know that my eyes adjust quite quickly to the dark. As well, I’ve never had a problem driving at night time.

  5. Stephani Roberts says:

    @Matthew My husband is color blind and he was able to spot deer in the fields last weekend as we drove home at twilight. They were almost invisible to me as they blended into their background but he saw them easily as distinct shapes. He speculated that it was a result of his color blindness. I think so. There are advantages, this could correlate with sharp shooting. He mentioned that color blind men were put at the front of the lines because they were able to spot camouflage. Here’s a short article about the upside of color blindness:

  6. marlene frykman says:

    @joe: wonderful. that is a fantastic tool. thanks for sharing!

  7. Joe Dolson (1152 comments.) says:

    @marlene Thanks for the tip! I’ve fixed the link.

  8. marlene frykman says:

    hi joe, just letting you know the link to the vision simulator is broken :(

  9. Joe Dolson (1152 comments.) says:

    @Matthew I’ve read that as well; but again, without any definitive evidence.

    @Karl What I wonder about that is whether that perception is because you’re more accustomed to identifying what you can see with reduced color or because you can actually see better. Given that one of the characteristics of low-light conditions is a significant reduction of color definition, I’m wondering whether the real issue is in the ability to understand what you’re seeing, rather than actually having improved perception in low-light conditions. From a subjective perspective, this may give you better understanding of your surroundings in low-light, but not actually mean that you have better vision. Does that make sense?

  10. Karl Groves says:

    re: Night Vision. I have no evidence, but I am very color blind (as in usually can’t get any of the items in the Ishihara tests) and I seem to have much better night vision than most people.

  11. Bryan (1 comments.) says:

    Thanks for clearing things out. Very good and interesting read.

  12. Matthew says:

    I’ve heard a similar rumor that colorblind individuals are better sharpshooters, with the justification being that your retina packs in more rods, which give you a higher resolution image. I’d like to see the Snopes on that one (although I still like to repeat it :) )

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