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And about 10% of men have difficulty telling red from green. No. "Red-green colorblindness" is an inaccurate and misleading name; "green weakness" is a better
by ubernostrum 16y ago
And about 10% of men have difficulty telling red from green.
No.
"Red-green colorblindness" is an inaccurate and misleading name; "green weakness" is a better description, and is what every doctor I've talked to uses as a casual name for the condition.
The best explanation I know of is to imagine the following: you're looking at a screen onto which is projected a square of pure red. Then, gradually, green is added, which will eventually cause the square to appear yellow (yes, red and green make yellow). When a person with "normal" color vision sees it as yellow, a person with the common forms of green weakness would still see it as a bit orange-ish.
In other words, the common form of "red-green colorblindness" doesn't cause a red sign to look green, or a green light to look red, or grass to look red, or any of that stuff. It mostly causes problems in the yellow part of the spectrum (one reason why I tend to avoid earth tones).
- BoppreH 16y agoIt might have been a different condition, but I could swear I saw a page of a guy who made a side by side comparison of images that for him looked the same. I clearly remember two pictures, one depicting very bright red berries on a bush and other with the berries colored green, almost invisible now.
- zephyrfalcon 16y agoMaybe this page: http://critiquewall.com/2007/12/10/blindness http://critiquewall.com/2007/12/10/blindness
- BoppreH 16y agoExactly that one. Thanks. So, is that a different condition?
- zephyrfalcon 16y agoHmm. I'm not sure. I am R/G colorblind myself, and I don't confuse red and green traffic lights; they look completely different to me. On the other hand, some devices use LEDs that can be red or green (like the Nintendo DS; red means it's time to charge the battery), and I can't tell them apart at all. Also, for what it's worth, on my MacBook the images in the aforementioned blog post look almost the same to me. But I looked at them on a different computer as well, a netbook where I tweaked the color settings, and there they don't look the same at all. (I still can't pass the Ishihara test on that one though... :-)
- nitrogen 16y agoI have a relative who doesn't perceive red as a color at all, only as a change in brightness when it is added to or removed from an image. Presumably he still perceives red lights as having some sort of color and not just gray, but it isn't red.
- ubernostrum 16y agoProblems with brightness usually are a result of protanopia or protanomaly, which are much rarer than what most people mean by "red-green colorblindness" (which is usually deuteranomaly).
- btilly 16y agoLooking at http://colorvisiontesting.com/color2.htm http://colorvisiontesting.com/color2.htm confirms what you say, but also confirms that there are many kinds of color-blindness and about 2% of men really can't tell the difference between green and red. Not as many as I said, but still a significant fraction.
- ubernostrum 16y agoThere are three basic types of colorblindness, and two of them -- dichromacy and trichromacy -- break down into three subtypes each. When people say "red-green colorblindness" they almost always mean deuteranomalous trichromacy (AKA deuteranomaly, "green weakness"), which is A) by far the most common form of "colorblindness", B) for practical purposes mostly affects the yellowish part of the spectrum and C) is typically so mild that most people who are deuteranomalous could go their whole lives without ever knowing it. The problem is that the average person doesn't ever realize this -- just as you apparently believed that the most common form of colorblindness led to an inability to distinguish red from green -- and so there are a huge number of misconceptions floating around which, as one of those 6% of males who are deuteranomalous, I do my best to clear up whenever possible.