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Everything in the article, from start to finish, seems to make perfect logical sense. The problem is: to me, that perceptual colour wheel at the end does not a

Everything in the article, from start to finish, seems to make perfect logical sense. The problem is: to me, that perceptual colour wheel at the end does not appear to be perceptually uniform at all. The left hand side (yellow->green->blue) appears to vary far less than the right hand side (yellow->red->blue). To me, the artist's one at the top looks most perceptually uniform, despite not being quite right from a physics perspective. The physics based one, with red/green/blue and yellow/cyan/magenta equally spaced is somewhere in between for me. This probably explains the myth of yellow/red/blue being the primary colours – they appear most perceptually different. So why is that so if, by the sensible reasoning of the article, the wheel at the end should look most uniform? I don't know the answer to that. Maybe it's due to one of those later layers of processing mentioned? Maybe the non-uniformity is just baked into our brains for some evolutionary reason, to do with colours commonly encountered in the wild?

itishappy 2y ago
It's a shame the article doesn't go deep enough to encounter perceptual uniformity. In short, the human visual system is strongly non-linear. We perceive more greens than blues or reds. None of the color systems mentioned in the article (including the CIE 1931 chromaticity diagram at the end) are perceptually uniform. The 1976 color spaces (CIELuv and CIELab) were introduced as an attempt to deal with this, and there's been many other attempts since. My favorite is OKLab: https://bottosson.github.io/posts/oklab/ https://bottosson.github.io/posts/oklab/
- quietbritishjim 2y ago
  > We perceive more greens than blues or reds. As I said in reply to the sibling comment, this is essentially the opposite of my point: it seems to suggest that green should take up a disproportionately large part of the colour wheel (in fact, that's what the article's suggested wheel at the end does), but I'm saying it should take up less. But, as I mentioned in my other comment, an experienced perception of green looking similar to physically nearby colours is not necessarily related to our ability to "perceive more greens". I haven't seen OKLab before, thanks. But it seems to be more about the perceived lightness of different hues, which is something different again.
  - itishappy 2y ago
    You're right, I have it flipped. We see fewer greens and more blues. https://en.wikipedia.org/wiki/Color_difference https://en.wikipedia.org/wiki/Color_difference https://en.wikipedia.org/wiki/Color_difference#/media/File:CIExy1931_MacAdam.png https://en.wikipedia.org/wiki/Color_difference#/media/File:C... You probably be more interested in or CIELab. OKLab builds off this and tries to fix lightness. https://en.wikipedia.org/wiki/CIELAB_color_space https://en.wikipedia.org/wiki/CIELAB_color_space The Munsell Color system is also pretty cool. https://en.wikipedia.org/wiki/Munsell_color_system https://en.wikipedia.org/wiki/Munsell_color_system
viridian 2y ago
Your intuition is right, and can be explained by looking at both the visible spectrogram and also the CIE diagram. In the former, what we call green takes up an inordinate amount of the spectrum. In the latter, green clearly takes up the largest amount of area of any well defined color. Your eye is most receptive to green, in both the narrow and broad sense. The absolute peak is a green, and of any reasonable, well defined broad grouping of spectra, the greenest one is the one your eye will be most receptive to. Also interestingly, the two colors that dovetail into colors we cannot see on either end, red and violet, we are the least receptive to. You can see this play out in real survey results from XKCD: https://blog.xkcd.com/2010/05/03/color-survey-results/ https://blog.xkcd.com/2010/05/03/color-survey-results/
- quietbritishjim 2y ago
  > Your intuition is right ... Your eye is most receptive to green ... of any reasonable, well defined broad grouping of spectra, the greenest one is the one your eye will be most receptive to. Hmm, but doesn't that disagree with my intuition? Unless I misunderstood you? I'm saying green looks similar to nearby colours so should take up less space on a perceptual colour wheel (e.g. blue and green look much more similar than blue and red to me, so blue and green should be much closer to each other). But you're saying we can perceive many shades of green, presumably with the implication that it should take up more space on perceptual colour wheel. That xckd article seems to agree with me: a huge chunk of the physical colour space is simply lumped into "green", rather than given lots of different names at you'd expect if different bits appeared visually distinctive. In fact, this all is not necessarily a contradiction: perhaps we can distinguish between extremely similar shades of green, better than other colours, but experience even very different shades of green as feeling subjectively similar.

itishappy 2y ago

It's a shame the article doesn't go deep enough to encounter perceptual uniformity. In short, the human visual system is strongly non-linear. We perceive more greens than blues or reds. None of the color systems mentioned in the article (including the CIE 1931 chromaticity diagram at the end) are perceptually uniform. The 1976 color spaces (CIELuv and CIELab) were introduced as an attempt to deal with this, and there's been many other attempts since. My favorite is OKLab: https://bottosson.github.io/posts/oklab/ https://bottosson.github.io/posts/oklab/

quietbritishjim 2y ago
> We perceive more greens than blues or reds. As I said in reply to the sibling comment, this is essentially the opposite of my point: it seems to suggest that green should take up a disproportionately large part of the colour wheel (in fact, that's what the article's suggested wheel at the end does), but I'm saying it should take up less. But, as I mentioned in my other comment, an experienced perception of green looking similar to physically nearby colours is not necessarily related to our ability to "perceive more greens". I haven't seen OKLab before, thanks. But it seems to be more about the perceived lightness of different hues, which is something different again.
- itishappy 2y ago
  You're right, I have it flipped. We see fewer greens and more blues. https://en.wikipedia.org/wiki/Color_difference https://en.wikipedia.org/wiki/Color_difference https://en.wikipedia.org/wiki/Color_difference#/media/File:CIExy1931_MacAdam.png https://en.wikipedia.org/wiki/Color_difference#/media/File:C... You probably be more interested in or CIELab. OKLab builds off this and tries to fix lightness. https://en.wikipedia.org/wiki/CIELAB_color_space https://en.wikipedia.org/wiki/CIELAB_color_space The Munsell Color system is also pretty cool. https://en.wikipedia.org/wiki/Munsell_color_system https://en.wikipedia.org/wiki/Munsell_color_system

viridian 2y ago

Your intuition is right, and can be explained by looking at both the visible spectrogram and also the CIE diagram. In the former, what we call green takes up an inordinate amount of the spectrum. In the latter, green clearly takes up the largest amount of area of any well defined color. Your eye is most receptive to green, in both the narrow and broad sense. The absolute peak is a green, and of any reasonable, well defined broad grouping of spectra, the greenest one is the one your eye will be most receptive to. Also interestingly, the two colors that dovetail into colors we cannot see on either end, red and violet, we are the least receptive to. You can see this play out in real survey results from XKCD: https://blog.xkcd.com/2010/05/03/color-survey-results/ https://blog.xkcd.com/2010/05/03/color-survey-results/

quietbritishjim 2y ago
> Your intuition is right ... Your eye is most receptive to green ... of any reasonable, well defined broad grouping of spectra, the greenest one is the one your eye will be most receptive to. Hmm, but doesn't that disagree with my intuition? Unless I misunderstood you? I'm saying green looks similar to nearby colours so should take up less space on a perceptual colour wheel (e.g. blue and green look much more similar than blue and red to me, so blue and green should be much closer to each other). But you're saying we can perceive many shades of green, presumably with the implication that it should take up more space on perceptual colour wheel. That xckd article seems to agree with me: a huge chunk of the physical colour space is simply lumped into "green", rather than given lots of different names at you'd expect if different bits appeared visually distinctive. In fact, this all is not necessarily a contradiction: perhaps we can distinguish between extremely similar shades of green, better than other colours, but experience even very different shades of green as feeling subjectively similar.