Why we're blind to the color blue

One of my favourite series in art is Yves Klein's blue work. For anyone unfamiliar, he found a blue that he considered the bluest possible blue [1], and went on a journey painting everything in that blue. I loved that he did this, and then eventually managed to get to an exhibition of his work at the Tate Modern and was absolutely blown away by it - it really needs to be seen in the flesh to appreciate it. There's something about his blue, that when painted on to a sculpture, almost makes the 3D disappear and the sculpture looks 2 dimensional. Extremely beautiful.

As a side note, some (many?) cultures around the world have no word for blue, blue is just other shades of green.

[1] https://en.wikipedia.org/wiki/International_Klein_Blue

I don't believe the blurred images at the end have anything to do with eye focus, as the author suggests.

After all, chromatic aberration is blurring of only a very, very small amount.

The demonstrated seemingly negligible perceptual effect of blurring blue to a huge degree in a multicolor image doesn't seem to have anything to do with that, but rather the fact that we perceive primary blue as a much darker color than primary red or green, and we perceive differences in lighter colors much more easily.

If the author were correct that we have big problems focusing on blue, then we'd see that blue text against a black background would be massively blurry -- but it's simply not. It's comparatively low-contrast (because blue is a dark color), but it's nearly indistinguishably as sharp as red and green.

There's an optometry place in my neighborhood with a back-lit sign with big, blue block letters. And every time I walk by at night I note how fuzzy it looks.

I'm convinced this is an intentional troll. This optometrist knowingly picked a sign to make people momentarily question their vision.

Blue LEDs and black lights show this effect very clearly. This is e.g. described much more succinctly in the top comment here: https://www.reddit.com/r/askscience/comments/3c1qsg/why_do_b...

> 2 reasons: 1) You don't have the nearly as many short wavelength detecting blue cones as you do red and green in your fovea. 2) The angle of refraction is dependent on wavelength and short wavelengths get refracted more than relatively longer ones by your eye and therefore focus in front of your retina if you are myopic (nearsighted). The black lights are throwing off a ton of very short wavelength light and when coupled with the larger pupil you have in the dark it sets your eye up for a bunch of chromatic aberration. They should look clearer if you are hyperope or overcorrected in your myopic prescription, or if you view them at a closer distance.

I would guess the deeper reason is that the sky is blue. That makes it more useful to have good vision in red and green.

If we needed good resolution everywhere, we might have had eyes optimizing for different colors, four eyes, etc.

Also, it isn’t as simple as this article describes. The human eye can vary its focal distance (https://en.wikipedia.org/wiki/Accommodation_(eye)) over a larger range than the effect of color aberration, so the eye _could_ optimize for having optimal focus for blue light or vary that over time.

(https://www.osapublishing.org/josa/abstract.cfm?uri=josa-68-... indicates humans can learn to do that in the lab)

Could this be a factor in why we didn’t evolve to see a wider range of wavelengths?

Is the visual spectrum just barely within the range that our brains can correct for the diverging focal lengths without needing additional lenses or modifications to the eye?

The second to last demonstration blows my mind. I can't help but feel like I'm being duped, the result is so sharp.

This is amazing to see. We should use this for image optimization. When we compress channels, we should compress the blue channel to like 30% while keeping others at fairly large 80% and it might appear better than a 60% compressed image.