
Impossible Colors - arseny-n
https://en.wikipedia.org/wiki/Impossible_color
======
tgb
I've used this as an example of (non)-vector spaces in a linear algebra class
before. Light perception is based off the stimulation of three color cones, so
three (positive) values. The light available to us stimulates those cones in
certain ways and three light colors are enough to form a "basis" of the space
of perceived colors. But the fact that the values are always non-negative
means that there are possible cone-stimulation values that are never
achievable by our light.

However, super-saturating your eyes with a color and then removing the
stimulus effectively allows you to also "subtract" out some light and
therefore reach parts of the perceivable-color-spectrum otherwise
unobtainable.

I thought it was a clever application but my students didn't seem too
impressed!

~~~
andrewmcwatters
It's interesting to think you've almost certainly then impressed more people
with this knowledge just posting it online here.

Thanks for sharing, what a neat thing!

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terramex
If you have a VR headset, I recommend playing around with showing different
colors to either eye. You can get some really nice iridescent effects, very
hard to achieve in real life and impossible on flat screen (well, you can
cheat a bit by doing a cross-eye 3D image). Be sure to try both complementary
and analogous colours and put iridescent objects into ordinarily looking
environment, if you simply change colour balance on one eye camera the effect
will be too unpleasant.

~~~
chrisweekly
what VR setup would you recommend for someone without any? I've got a ps4. I
don't want to overspend on deprecated / imminently-obsolete gear, but would
love to experience it at home. is there a sweet spot beyond "toy" level but
short of $$$$?

~~~
terramex
If you are fine with Facebook then Oculus Quest is the sweet spot at the
moment. It does not have photorealistic rendering like PC-based VR but it is
self-contained, does not need a PC but can be connected to a PC to play PCVR
titles, has solid library on its own and being wireless is huge advantage.
There are strong rumours that they will announce new Quest model on September
16th at base price of 299$ - but do not quote me on that.

I'd avoid PSVR, it is obsolete in 2020.

~~~
silicon2401
what about the valve index? Oculus' facebook connection makes it flat out not
in consideration for me

~~~
falcolas
The index is great, honestly. The knuckle controllers are fantastic (though
there's some issues with the surface mounted joysticks not having great
longevity), the HMD is fantastic, and the support seems pretty top notch (bad
controllers being RMI'd).

The biggest thing seems to be the long lead times between ordering and
arrival.

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EE84M3i
Something this reminds me of is the mccollugh effect.

WARNING: the following link contains a literal infohazard basalisk image that
if stared at for a few minutes will alter your color perception for a
significant period of time - potentially months. It is not behind a spoiler,
which would be against the rules on English Wikipedia

[https://en.m.wikipedia.org/wiki/McCollough_effect](https://en.m.wikipedia.org/wiki/McCollough_effect)

~~~
Metacelsus
>It is not behind a spoiler, which would be against the rules on English
Wikipedia

On the desktop site it has a spoiler box saying, "Show at your own risk."

~~~
EE84M3i
That's funny. It didn't for years up to at least a month ago or so and also
doesn't seem to on mobile now for me, but I didn't check it on desktop before
posting the comment!

Edit: it was hidden Aug 16th[1] but previously hiding it has been
reverted[2][3][4] for at least 2 years per WP:DISC[5]

[1]:
[https://en.wikipedia.org/w/index.php?title=McCollough_effect...](https://en.wikipedia.org/w/index.php?title=McCollough_effect&diff=973267966&oldid=969390752)
[2]:
[https://en.wikipedia.org/w/index.php?title=McCollough_effect...](https://en.wikipedia.org/w/index.php?title=McCollough_effect&diff=885452869&oldid=885217380)
[3]:
[https://en.wikipedia.org/w/index.php?title=McCollough_effect...](https://en.wikipedia.org/w/index.php?title=McCollough_effect&diff=879014653&oldid=878883404)
[4]:
[https://en.wikipedia.org/w/index.php?title=McCollough_effect...](https://en.wikipedia.org/w/index.php?title=McCollough_effect&diff=845979838&oldid=841436792)
[5]:
[https://en.wikipedia.org/wiki/Wikipedia:Content_disclaimer](https://en.wikipedia.org/wiki/Wikipedia:Content_disclaimer)

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jasode
Fyi on a semi-related topic I learned from a fascinating Youtube video... the
color "brown" is a psychological construct[0]. But from an RGB perspective ...
there's no such color as "brown"; it's actually just "orange" in a particular
context:
[https://www.youtube.com/watch?v=wh4aWZRtTwU](https://www.youtube.com/watch?v=wh4aWZRtTwU)

[0] pedantic alert: yes "every color" is ultimately a mental construct of the
brain but hopefully you know what I mean

~~~
formerly_proven
This is based on the simplistic view that hue equals color. Modern perceptual
color models like CIECAM02 define "color" through a much larger number of
influences.

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optimalsolver
As neuroscience advances, what is the likelihood of _truly_ novel color
experiences?

I don't mean discerning ever finer gradations in existing colors, but entirely
new color qualia.

What would it be like? Would our brains be able to integrate this new
phenomenal experience?

And most importantly, if color is a property of brains rather than something
in the external world, does that imply the number of "possible colors" is
infinite? I.e. seeing as biological brains "choose" how to internally
represent a particular wavelength of EM radiation, is the seemingly Platonic
realm from which these colors are plucked from inexhaustible?

We currently have aesthetic preferences over existing colors. I would want to
know whether these possible colors can be enumerated, searched through, and
have a utility function placed over them so that each human can find what is
to them "the best possible color."

~~~
enriquto
> As neuroscience advances, what is the likelihood of truly novel color
> experiences?

No need for neurosciences, just some fancy spectral filters like those on IMAX
3D glasses. With some practice using these glasses you can experience a six-
dimensional color space. When you remove your glasses, this six-dimensional
space collapses into the common three-dimensional color space. But with the
glasses, you can distinguish many different colors that look exactly the same
to regular humans. That white wall? It looks a perfectly uniform white to most
people, but you can see clearly that two very different kinds of white have
been used here and there.

A similar effect can be obtained indoors by lighting objects with
monochromatic lights, but it is not as dramatic as with glasses.

~~~
pueblito
I used to work in highway paving, and I learned how to tell the temp of
asphalt with polarized sunglasses. It's not the same as a truly novel color
experience but its a neat party trick

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umvi
I highly recommend this Captain Disillusion video about color if you want to
learn more about color theory:
[https://youtu.be/FTKP0Y9MVus](https://youtu.be/FTKP0Y9MVus)

You may have to watch the video multiple times though, because the information
comes out of a firehouse.

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yboris
My favorite ever "Impossible Color" illusion:

 _Eclipse of Titan_

[https://www.skytopia.com/project/illusion/ipage-
et.html](https://www.skytopia.com/project/illusion/ipage-et.html)

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roenxi
Don't miss the link down the bottom -
[https://en.wikipedia.org/wiki/Tetrachromacy](https://en.wikipedia.org/wiki/Tetrachromacy)
\- human perception of colour varies wildly between different people.
Basically the opposite of colour blindness.

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dang
If curious see also

2011
[https://news.ycombinator.com/item?id=2273081](https://news.ycombinator.com/item?id=2273081)

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nmeofthestate
Can anyone see "yellow-blue" as mentioned in the article? When I try, it just
cycles (although not discretely) between yellow and blue.

~~~
ddingus
Try it when you are really tired, and or after having some good sativa, if
that is safe and appropriate for you.

I find my mind extremely receptive to these sorts of things when I'm very
tired on the edge of sleep.

A good sativa actually opens up quite a bit of pattern recognition and other
subtle visual perceptions. One example I can think of is a cardboard box that
actually has the manufacturer's logo lightly embossed. You can't really see it
at least I never did. But one evening after a good meal and the sativa, I
looked at that box and could totally see the subtle difference in the circle
for the carport. Interesting lie, I have remained able to see it. Like a
little doorway opened.

~~~
ddingus
Past edit time error correction:

>looked at that box and could totally see the subtle difference in the surface
of the cardboard. Interestingly, I have remained able to see it.

