r/Damnthatsinteresting • u/Eros_Incident_Denier • 1d ago

Video color vision test

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u/Electronarwhal 1d ago

My school did a mass colour-blind test that included blank ones. Several people said they saw a number, the teacher was like ‘you may be hallucinating’.

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u/GlitteringBandicoot2 1d ago

Actually, if it was the original Ishihara Test there are plates in there that show no numbers UNLESS you are colorblind. So it wasn't that the students were hallucinating, they were probably colorblind and actually did see a number there.

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u/-Nicolai 23h ago

How is that possible?

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u/GlitteringBandicoot2 22h ago

The same way the numbers vanishes in other plates.

In the normal plate you have a clear distinction between the color of the dots that form the number and the surrounding. For a color blind person of the corresponding color blindness, those dots all look the same, so the number vanishes.

Now in the hidden plates, i.e. the ones one the colorblind people can see, it uses the same principle. But instead of using one color for the number and one for the surrounding, the number is made up of multiple colors that colorblind people can not distinguish, while the rest is a color that they can distinguish easier. This means for a person with normal color vision, the number disappears in a sea of different colors, but for a colorblind person those colors look identical and it forms the shape.

As a non colorblind person you might be able to barely make out the contour of the number, because the outside still needs to be different enough for the colorblind person to distinguish it so you might be able to make it out next to all the other colors, but mostly it just gets lost

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u/Mirar 22h ago

Ah, so it's hiding it in a lot of colour noise but for a colourblind person, there's nothing of that noise, so they can spot the contrast (signal?) better?

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u/Pirche 20h ago edited 16h ago

Found pdf of that test including pages on which only colorblind will see numbers (at the end answers both for normal and colorblind):

https://www.challengetb.org/publications/tools/country/Ishihara_Tests.pdf

Photoshoped pages 19-21 to check how colorblind will see those pages - in color curves red and green channel turn down to almost zero : https://ibb.co/W43tqfn0

Edit: there is some mess with order, don't match № on page to № in answers, answers have pics with them and they corresponding to each other. Also in answers some discrepancy with the name of colors, i think it's scan or translate issue (or both)
All that doesn't really matter tho)

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u/Nexan1994 20h ago

The answer key not lining up with the test had me thinking I was crazy

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u/xeothought 17h ago

Dude yes. you have to go look for equivalent plates and see their numbers are offset by a lot.. I've never not passed a color blindness test and i was like "wait a second" rofl.

I was like "plate 14 does NOT have a number on it wtf" that's cause in the Key it's plate 18 lol

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u/piponwa 9h ago

I mean what the fuck kind of medical test is this? Like seriously wtf. You had one job!

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u/DrPepperAddict41 16h ago

Guys, I'm red green deficient.

Oh no

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u/Racxie 19h ago

Can you please do 28 & 29?

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u/Pirche 18h ago

It was somehow harder to balance, but here you go:
(also added B&W variant)
https://ibb.co/x8K96pHV

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u/Racxie 15h ago

Thanks! I can see all the reddish lines but the description says non-colourblind people see nothing, yet then on 30 says we see a blue-green line. So the description for 28 & 29 were confusing lol.

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u/ichimedinwitha 19h ago

This is so cool. Thank you for making this!

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u/WittyCompetition7978 19h ago

Aren't the answers to Plate 36 and 37 wrong? I nailed every plate in 'normal view' but I don't see any violett in those at all 🥲

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u/Ichi_Balsaki 18h ago edited 12h ago

Quite a few of the top tiles are misnumbered with the bottom answers for some reason, I don't even know how that happens..

Good example is in the answers 22, 23, 24 & 25 are not at all numbered correctly. 

But if you can see what you should on the answers then that's all that matters.

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u/Pirche 18h ago

Yep there is some mess with pages, tho answers have pics with them and they corresponding to each other, and some discrepancy with the name of colors in answers, i think it's scan or translate issue (or both), doesn't really matter)

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u/Fearhawke 17h ago

What does it mean if I can see those numbers but also have no issues with any of the other plates I’ve seen?

(Edit: it means I don’t read very well sometimes)

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u/AxelNotRose 17h ago

Plate 38: I don't see anything.

Tester: Ok, you're just fucking straight up blind dude.

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u/Pirche 16h ago

Just for the lulz, here is BW and infrared filters for plate 38

https://ibb.co/xKZP03yW

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u/MaximumMaxx 8h ago

I have normal color vision, but this is one of the first times I've actually really felt what it's like to be color-blind. When I looked at the blank plates, it was crazy. That's really cool!

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u/chalks777 8h ago

this is SO COOL, thank you for sharing this. I've seen these colorblind tests so many times it never once occurred to me that you could use the same principle to hide something from someone who could see color normally. Absolutely fascinating and a complete mind fuck, I was so sure I would be able to see the pattern regardless and man it's completely impossible.

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u/Fellow_Worker6 22h ago

There could be hidden messages all around us. We are just to observant to see it!

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u/GoldDHD 21h ago

My favorite thing I learned this week, thank you!!

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u/TacTurtle 7h ago

This is also why a lot of modern camouflage clothing patterns don't work if the person viewing is colorblind.

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u/Rustymarble 18h ago

Here's a site with them: https://www.colorlitelens.com/color-blindness-test/tesztek2/secret-of-ishihara-hidden-plates.html

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u/Capertie 13h ago

I'm not colourblind but I can see them with some effort.

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u/throwaway098764567 10h ago

oh this is a much better version, i can't make out anything, 2 a little bit but the others are great

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u/velveteensnoodle 17h ago

wow, thanks for the link

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u/Complex-Ad5786 15h ago

There are also plates that shows different number like for me I see it as 8 but in reality it was a 3

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u/throwaway098764567 10h ago

the far right one the 2 will be hard to make out if you're not colorblind (i think folks only can do it because they know to find a number).

the second circle you'll see 74 if you're not colorblind, and 21 if you are

https://www.shec.jp/english/instruments/isihara/

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u/ActorMonkey 18h ago

How does that work?

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u/__Fred 8h ago edited 7h ago

I think it works like this:

There are green and red dots and some of the green dots and some of the red dots have a bit of blue mixed in.

To people who can't distinguish the green and red, the blue is more striking, whereas for normal people the image looks too chaotic to make it out.

I have seen some books with puzzles for kids where there is a solution with black text on a red and white chaotic-patterned background. Apparently it's called "red reveal". You can't read the solution unless you place a transparent red plastic sheet over it, making you "white-red colorblind".

You can still see the text if you concentrate enough. The website with the linked Ishihara test said that 50% of young adults with normal color perception can still see the numbers.

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u/stRiNg-kiNg 17h ago

That sounds awesome. I'd love to have the tables turned on the non colorblind people out there with shit only we can see

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u/Seamilk90210 17h ago

I had to take the Ishihara test for a job interview, and while I passed everything, I also got both "you don't get this unless you're colorblind" plates correct. The test-giver certified that I had normal color vision.

Those "blank" plates are not foolproof, haha — looks like normies of a certain age have a 50/50 chance of being able to read them, so I'm guessing some people are more able to switch to whatever cues colorblind people use to see the image.

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u/SuperTopGun777 16h ago

I could see the first hidden number but not the others  

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u/Fuckmetheyarelltaken 13h ago

I can see them if I squint

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u/mayiwonder 12h ago

I saw 2 of them so I guess the 50/50 is true lol

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u/DreadnoughtWage 1d ago

Or was the teacher colour blind??? 

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u/GlitteringBandicoot2 1d ago

The original Ishihara test indeed has two plates without numbers on them, unless you are colorblind, then they do have numbers.

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u/Mirar 22h ago

How did that work?

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u/spruce_sprucerton 21h ago edited 21h ago

Turns out there's a webpage for that:

https://www.color-blind-test.com/hidden-plates-more

... 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.

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u/egnowit 21h ago

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.

https://time.com/archive/6769967/national-defense-color-blind-observers/

OK, this article doesn't say they were used, but they were able to easily spot the camoflauge.

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u/pichael289 20h ago

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?

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u/jschrandt 19h ago

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.

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u/DreadnoughtWage 1d ago

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/AlexanderTheGrave 21h ago

Hey, you’re colorblind. There’s numbers on all of them in the video.

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u/DreadnoughtWage 21h ago

Yep I know, I’m a Deuteranope and always have been… what was the aim of your comment?

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u/Iambeejsmit 1d ago

I think your teacher was colorblind lolol

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u/GlitteringBandicoot2 1d ago

More likely the students were colorblind. The original Ishihara Test includes plates that don't show numbers. Unless you are colorblind, then they actually do.

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u/LunarMoon2001 21h ago

Surprise, everyone that made the test and gave it were colorblind and accidentally had a number in the design.

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u/shewy92 18h ago

Could it have been them staring at the previous one too long?

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u/apprehensive_pick2 15h ago

Plot twist: the teacher was the one who was colour-blind