While it is true that some saturated blue-green colors will never be reproducible with only 3 primary colors, the CIE 1931 chromaticity diagram used in TFA overemphasizes their importance, because human vision cannot distinguish many colors in that area of the diagram.
In reality, the greatest defect of the sRGB color space, which is still too frequently the default color space, is that it is not able to reproduce many saturated orange/red/purple colors, which are very frequently encountered around us, e.g. in flowers, fruits and clothes.
The missing orange-red-purple corner appears small in the diagram in comparison with the missing blue-green corner, but in reality humans perceive much more different colors in the orange/red/purple corner, so the relation between those areas would be opposite in a uniform color space.
The Display P3 color space is much better than sRGB for reproducing orange/red/purple colors and now it is available even in many cheap monitors. However many monitors that can reproduce Display P3 come configured by default to use just sRGB. Such monitors should always be reconfigured to use Display P3.
Monitors that can reproduce an even greater part of the Rec. 2020 color space are obviously better than those that can do only Display P3, but such monitors with a higher color gamut are usually more expensive. The full Rec. 2020 color space can be reproduced only with laser projectors, because it uses monochromatic primary colors.
> the relation between those areas would be opposite in a uniform color space.
If I understand correctly fig. 3 in [1] should be perceptually uniform. The bluegreens missing from sRGB, but present in BT.2020 comprise a sizeable chunk comparable to redyellows.
I took up acrylics painting a few years back and I've been surprised by how much is lost in photos and videos. The two colors with which I've noticed this the most are ultramarine blue and prussian blue. I don't think it's just the color though, part of it comes down to how light is reflected off the painting and where you're standing, as well as the texture and the brush strokes. I have a few paintings hanging in my room and occasionally I'll look at them for a while and it'll reveal a new perspective to me that I had previously missed, despite being the one who made it.
This post is making me feel a bit inspired to go outside and immerse myself in the forest to take in the greens. Thanks for sharing.
What I missed in the article: the curves of the three “cone kinds” overlap. What if you could stimulate kinds of cones individually to see entirely new colors? Some people shoot layers at them into eyes. But you can also try this website: https://dynomight.net/colors/ (previously on HN but search fails me).
Through the magic of liner algebra it turns out that you can stimulate cones independently even with normal displays. Search for 'silent substitution'!
Really nice article, I'll look closer to green lights next time I see one.
The most striking experience I had was working with a blue laser (430nm). The best way I found to describe its color is that it was screaming "blue" at me. Since then, I'm always disappointed when looking at a screen displaying #0000FF.
"This is a good time to spare a thought for our red-green colorblind brethren. [...] it is to them that we owe the beautiful color of green traffic lights. The spectral requirements that make the green signals distinguishable from red in their eyes make them beautiful in ours."
The phosphor screen of a B&O MX8000 TV (a Philips tube) was unlike any I’ve ever seen in terms of cyan intensity. That was in 2020 while the tv is from the 1980’s. Playing Donkey Kong on it was totally different than any other screen. It was like a Morpho butterfly, but in the article it is pointed out that phosphor screens have limited color range.
Triangles between screens may differ with tuning, but I suppose they all are limited in range. I’ve yet to experiment if this experience was a “brand experience” because I liked the TV or that the colors are indeed more intense than even some HDR/DV flat screen from the past few years.
This article was so well written that it gives a lot of energy to make this comparison for real. Absolutely masterful writing and all of the plenty examples make me want to look for colors I’ve missed out on while watching so many screens.
What the article does very well is vibrantly describe what you are missing and then post an image of it, such as a beach. Looking at that image, it falls absolutely flat compared to memories and the imagination of those places. This makes it tangible how limited screens really are.
ACES AP0 is the only color space I know that is designed to represent all possible visible colors. It's a purely theoretical color space, though. The widest color space designed for actual implementation, Rec. 2020, still can't faithfully show most of the natural greens and cyans, like your green laser pointer.
Its unclear to me why the color space is 2-dimensional. Why wouldn't it be a 3-dimensional space, indexed by how much each of the 3-cones is activated ? Not clear to me from the article!
It is 3 dimensional. That commonly repeated CIE diagram is a 2d slice of the color volume. Since 1931 that diagram is obsolete, misleading, and fails at a lot of modern color science, and has been replaced many times, but is what many people go to. The most recent replacement (well, by CIE), is CIE 2015. Comment on it [1]
Modern color modeling is much richer then 3 parameters, because human vision is much more complex than simply color frequencies. CIE 1931 was low brightness, 2 degree field of vision, center of vision derived. As brightness increases, color perception shifts. Colors are NOT linear; sRGB and CIE 1931 chose such a small section of human vision that they approximate that section with a linear assumption. Modern CIECAM models are not linear, are not 3 parameter, because color is not linear (CIECAM02 is 6 parameter [2], there are several after that one). A century of experiments, wide color gamuts, HDR, have thrown out CIE 1931 as a good model. It’s only momentum now, and slowly higher end things are replacing it.
A good introduction is Color Appearance Models, by Mark Fairchild, also any of his technical papers give a starting point into the science.
It is, inasmuch as we have 3 types of cone, which is an inherent orthogonality. It is also not, inasmuch as each cone is a wavelength in the same spectrum.
Either way, you can project a volume onto a plane, which is great for communicating visual data on paper or screen.
The interesting question is "why that arc in particular"; my ignorance will shine through if I speculate.
I assume that the projection encodes something about our relative perception of each cone's band, hence the big green corner.
>indexed by how much each of the 3-cones is activated
This will actually differ from person to person. If you look at a pure yellow wavelength light next to a red/green light mixed such that they create the exact same perceived yellow to you, it will look different to another person.
Aside from that, not really sure what a 3d view with the dimensions being r,g,b would actually offer
There are three cones, but there is an additional constraint that we plot the colors at maximum summed luminosity. So for one cone you would just have a point; two would show a line from 0% cone A+100% cone B -> 100% cone A; three is a plane
> Nearly every species of scorpion intensely fluoresces under UV light. […] Scorpions have photoreceptors in their tails, separate from their eyes. […] It is hypothesized that a scorpion uses this fluorescence to tell whether any bit of its body is left exposed from its hiding place. Its tail “looks” down at its body, and if it sees its own fluorescence, it knows it is exposed to light, and in danger.
And a special call-out to the “Andean Cock-on-a-Rock” :), see a photo in the article.
Very well written, super interesting topic. I never understood all these natural reasons why real life colors feel so much more vivid. I guess when I look outside of the rgb triangle in the graphic, the cyans/blues/greens shown (since I'm seeing this on a screen) are sort of shadow colors? Approximations without the full vibrancy?
Great article. Small nitpick though: while I understand that P3 deserves specific mention because it’s so ubiquitous now, it’s not like Apple invented the idea of wide-gamut displays. Adobe RGB, commonly used by wide-gamut computer monitors, in particular is noteworthy in the context of this article because it extends further into the blue-cyan-green than P3,
Impressionist paintings used a lot of synthetic ultramarine, they look very different IRL. There is a whole room in the Orsay museum where paintings seem to glow from the inside in the dark.
I do have a question that the article doesn't seem to attempt to answer, though. The article says (paraphrased in my new understanding) that any spectra which makes the cones in your eyes react the same way will result in seeing the same colour. Do we know of any examples of this?
(Colour-blindness seems like an obvious example; I'm curious though if there are any examples of two common scenarios where it can be demonstrated that there are different spectra in each, and yet most people will see them as the same colour.)
This is called metamerism. It can be a practical issue if two pigments have the same color under one light source, but a different one under another. You want your artificial teeth to have the same color as your real teeth in sunlight, led light, and a classic lightbulb for example.
Well, now that you mention it, I'd just like to remind you that people are a lot weirder than you might think! Having incisors to be a different colour (say, a brilliant red) under artificial lights could definitely be a thing people desired..
Would not the definitive answer to this be a computer screen.
On one side you have an apple, illuminated by natural sunlight. it fills your eye with a rich texture of subtly mixed frequency's covering the whole gamut of visible and invisible light. On the other a picture of an apple composed of brutal pure frequencies only emitting at 430, 540, 570 Nm. Can you tell the difference?
That makes sense. I feel a little silly that that's not something I considered despite the article saying exactly that. I think I got caught up in the details.
Well, the most common example si precisely screens, no? A screen displaying the color yellow is actually a spectrum of red and green peaks, stimulating your red and green cones just like a spectrum containing a single frequency of the color yellow.
Ultramarine pigment is too blue for your screen to replicate properly, for example. I don't know if there's a pigment that reflects only 520nm light, though.
I once abseiled into a crevasse while in Antarctica. The colours I saw in there were utterly breathtaking and I never knew why. Now I do, and this also tells mewhy the photos don't even remotely do it justice (aside from not being as big and three dimensional!)
Thanks for such a beautiful article about not looking at a screen: I'm off outside... :)
What an truly incredible article, particularly the way the color space diagrams are used to gradually tell the story (and the prose is great too). I actually want to read it again tomorrow morning in more depth.
In reality, the greatest defect of the sRGB color space, which is still too frequently the default color space, is that it is not able to reproduce many saturated orange/red/purple colors, which are very frequently encountered around us, e.g. in flowers, fruits and clothes.
The missing orange-red-purple corner appears small in the diagram in comparison with the missing blue-green corner, but in reality humans perceive much more different colors in the orange/red/purple corner, so the relation between those areas would be opposite in a uniform color space.
The Display P3 color space is much better than sRGB for reproducing orange/red/purple colors and now it is available even in many cheap monitors. However many monitors that can reproduce Display P3 come configured by default to use just sRGB. Such monitors should always be reconfigured to use Display P3.
Monitors that can reproduce an even greater part of the Rec. 2020 color space are obviously better than those that can do only Display P3, but such monitors with a higher color gamut are usually more expensive. The full Rec. 2020 color space can be reproduced only with laser projectors, because it uses monochromatic primary colors.
If I understand correctly fig. 3 in [1] should be perceptually uniform. The bluegreens missing from sRGB, but present in BT.2020 comprise a sizeable chunk comparable to redyellows.
[1] https://www.researchgate.net/publication/345252499_Evaluatin...
This post is making me feel a bit inspired to go outside and immerse myself in the forest to take in the greens. Thanks for sharing.
The most striking experience I had was working with a blue laser (430nm). The best way I found to describe its color is that it was screaming "blue" at me. Since then, I'm always disappointed when looking at a screen displaying #0000FF.
Triangles between screens may differ with tuning, but I suppose they all are limited in range. I’ve yet to experiment if this experience was a “brand experience” because I liked the TV or that the colors are indeed more intense than even some HDR/DV flat screen from the past few years.
This article was so well written that it gives a lot of energy to make this comparison for real. Absolutely masterful writing and all of the plenty examples make me want to look for colors I’ve missed out on while watching so many screens.
What the article does very well is vibrantly describe what you are missing and then post an image of it, such as a beach. Looking at that image, it falls absolutely flat compared to memories and the imagination of those places. This makes it tangible how limited screens really are.
Edit: added last paragraph
Modern color modeling is much richer then 3 parameters, because human vision is much more complex than simply color frequencies. CIE 1931 was low brightness, 2 degree field of vision, center of vision derived. As brightness increases, color perception shifts. Colors are NOT linear; sRGB and CIE 1931 chose such a small section of human vision that they approximate that section with a linear assumption. Modern CIECAM models are not linear, are not 3 parameter, because color is not linear (CIECAM02 is 6 parameter [2], there are several after that one). A century of experiments, wide color gamuts, HDR, have thrown out CIE 1931 as a good model. It’s only momentum now, and slowly higher end things are replacing it.
A good introduction is Color Appearance Models, by Mark Fairchild, also any of his technical papers give a starting point into the science.
[1] https://community.acescentral.com/t/cie-2015-cmfs-what-would...
[2] https://en.wikipedia.org/wiki/CIECAM02
Either way, you can project a volume onto a plane, which is great for communicating visual data on paper or screen.
The interesting question is "why that arc in particular"; my ignorance will shine through if I speculate.
I assume that the projection encodes something about our relative perception of each cone's band, hence the big green corner.
This will actually differ from person to person. If you look at a pure yellow wavelength light next to a red/green light mixed such that they create the exact same perceived yellow to you, it will look different to another person.
Aside from that, not really sure what a 3d view with the dimensions being r,g,b would actually offer
> Nearly every species of scorpion intensely fluoresces under UV light. […] Scorpions have photoreceptors in their tails, separate from their eyes. […] It is hypothesized that a scorpion uses this fluorescence to tell whether any bit of its body is left exposed from its hiding place. Its tail “looks” down at its body, and if it sees its own fluorescence, it knows it is exposed to light, and in danger.
And a special call-out to the “Andean Cock-on-a-Rock” :), see a photo in the article.
I do have a question that the article doesn't seem to attempt to answer, though. The article says (paraphrased in my new understanding) that any spectra which makes the cones in your eyes react the same way will result in seeing the same colour. Do we know of any examples of this?
(Colour-blindness seems like an obvious example; I'm curious though if there are any examples of two common scenarios where it can be demonstrated that there are different spectra in each, and yet most people will see them as the same colour.)
See the first minutes of this video, where he has a spectrum analyser: https://youtu.be/-DyrBDsKA5s?si=mRJPT2ecy6NqpB4N
On one side you have an apple, illuminated by natural sunlight. it fills your eye with a rich texture of subtly mixed frequency's covering the whole gamut of visible and invisible light. On the other a picture of an apple composed of brutal pure frequencies only emitting at 430, 540, 570 Nm. Can you tell the difference?
Thanks for such a beautiful article about not looking at a screen: I'm off outside... :)