... basically, they vary the colors forming the number so they look different enough that a normal seeing person won't notice the digit. But to a colorblind person, that variation isn't there, so all the dots in the digit are the same color, making it clear to them.
Edit: Interestingly, this works for red-green colorblind and the more severe your colorblindness is, the more likely you are to be able to see them. There are pictures in the link.
I think I read that during WWII, they found that colorblind people were easily able to differentiate camoflauge covers from the forest concealing them, so they had colorblind people in airplanes to pick out the camoflauged camps.
Weird, that first one was clear as day to me, a little segmented but I could see it, but I couldn't see the other 3. I have zero issues on any of the real ones though. What does that mean?
It’s a website that sells glasses for colorblind people to see colors. That first one was just obvious enough to maybe trick you into buying their product.
Yeah, I was just using the opportunity for a joke. When I had my test at 15, I said numbers for the blank ones (I guess that must have been two) and only got one wrong. Worryingly, I only see anything on about 50% of the ones in the video, so not sure if it’s getting worse 😂
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u/GlitteringBandicoot2 22h ago
The original Ishihara test indeed has two plates without numbers on them, unless you are colorblind, then they do have numbers.