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RGB is a color model[1], not a color space[2]. Note that the headline gets this wrong but the page linked to gets this right. sRGB or Rec2020 or ACEScg etc. a

RGB is a color model[1], not a color space[2]. Note that the headline gets this wrong but the page linked to gets this right. sRGB or Rec2020 or ACEScg etc. are color spaces with known primaries and a known whitepoint. This is not nit-picky. Almost everyone doing CGI for the first time w/o reading up on some theory beforehand gets this wrong (because of gamma and then premultiplication, usually in that order). Then there are color models which are also color spaces. CIE XYZ is an example. [1] https://en.wikipedia.org/wiki/Color_model https://en.wikipedia.org/wiki/Color_model [2] https://en.wikipedia.org/wiki/Color_space https://en.wikipedia.org/wiki/Color_space

zeroq 11mo ago
Not an expert but I'll drop my 2c Most of my career was somehow related to graphics programming and I always thought it's bit weird that most quantization algorithms were operating in RGB model despite the fact that it was designed for hardware, not so for faithful color manipulation. The easiest way to see that is to imagine a gradient between two colors and trying to make it in RGB. It doesn't seem right most of the time. If so, then why would we consider distance in 3D space between two colors as faithful representation of their likeness? Well, lo and behold, it's 2025 and everyone finally accepting LAB as the new standard. :)
- subb 11mo ago
  Except color is a construction of your eye-brain derived from stimuli, surround, memories, etc. It's definitely not something you can plug into a three-value model. Those are good stimuli encoding space, however. The distinction between brain-color and physical-color is what screws everyone up.
  - zeroq 11mo ago
    fun fact: there's a guy with similar background to mine, with similar dedication to color, yet way more productive and he came out with this incredible piece of art: rebelle app As with most recent technological breakthroughs it uses math from 1931 paper to magically blend colors in ways that seems so realistic it's almost uncanny.
  - dahart 11mo ago
    > It's definitely not something you can plug into a three-value model. What do you mean? And what is screwed up? We use 3 dimensions because most of us are trichromats, and because (un-coincidentally) most digital display devices have 3 primaries. The three-value models definitely are sufficient for many color tasks & goals. Three-value models work so well that outside of science and graphics research it’s hard to find good reasons to need more, especially for art & design work. It’d be more interesting to identify cases where a 3d color model or color space doesn’t work… what cases are you thinking of? 3D cone response is neither physical (spectral) color nor perceptual (“brain”) color, and it lands much closer to the physically-based side of things, but completely physically justifies using 3D models without needing to understand the brain or perception, does it not?
    - IgorPartola 11mo ago
      I had experimented with some photo printing services and came across one professional level service that offered pigment inkjet printing (vs much more common dye inkjet printing). Their printers had 12 colors of ink vs the traditional 4. I did some test photos and visually they looked stunning.
      - wongarsu 11mo ago
        "You only need three colors" is a bit of a cheat, because it doesn't really work out in reality. You can use three colors to get a good color gamut (as your screen is doing right now), but to represent close to every color we can see you would need to choose a red and blue close to the edge of what we can perceive, which would make it very dim. And because human vision is weird you would need some negative red as well, which doesn't really exist. Printing instead uses colors that are in the range we can perceive well, and whenever you want a color that is beyond what a combination of the chosen CMYK tones can represent you just add more colors to widen your gamut. Also printed media arguably prints more information than just color (e.g. "metal" colors with different reflectivity, or "neon" colors that convert UV to visible light to appear unnaturally bright)
        11mo ago
meodai 11mo ago
thanks for brining that up. Its a fight I stoped fighting a long time ago...
globular-toast 11mo ago
Is this why there appears to be a quite distinct plane inside the cube? If we were looking at them in the colour space would it look more uniformly spread?
adrian_b 11mo ago
While you are right, sometimes "RGB" is used as an abbreviation for some color space that is understood from the context, e.g. the CIE 1931 RGB color space (from which the CIE XYZ color space has been derived) or the RGB decoded correspondent of some TV color space, e.g. NTSC, PAL or SECAM.
- virtualritz 11mo ago
  I would really like to understand where that "sometimes" is, nowadays. RGB just means that color is expressed as a triplet of specific wavelengths. But what is red? And what does red = 1.0 mean w/o context (aka primaries & whitepoint)? What about HDR? What does green = 2.0 convey? Etc. For context, I worked in VFX production from the 90's to the early 2010's. About 25 years. And in commercially available VFX-related software, until the early 2000's, mostly, RGB meant non-linear sRGB, unfortunately (or actually: "whatever" would be more true). And it shows. We have VGX composed in non-linear color space with blown-out, oversaturated colors in highlights, fringes from resulting alpha blending errors, etc. A good compositor can compensate for some of these issues but only so far. If the maths are wrong, stuff will look shitty to some extend. Or as people in VFX say: "I have comments." After that, SIGGRAPH courses etc. ensured people were developing an understanding on how much this matters. And after that we had color spaces and learned to do everything in linear. And never looked back. Games, as always, caught up a decade after. But they, too, did, eventually.

zeroq 11mo ago

Not an expert but I'll drop my 2c Most of my career was somehow related to graphics programming and I always thought it's bit weird that most quantization algorithms were operating in RGB model despite the fact that it was designed for hardware, not so for faithful color manipulation. The easiest way to see that is to imagine a gradient between two colors and trying to make it in RGB. It doesn't seem right most of the time. If so, then why would we consider distance in 3D space between two colors as faithful representation of their likeness? Well, lo and behold, it's 2025 and everyone finally accepting LAB as the new standard. :)

subb 11mo ago
Except color is a construction of your eye-brain derived from stimuli, surround, memories, etc. It's definitely not something you can plug into a three-value model. Those are good stimuli encoding space, however. The distinction between brain-color and physical-color is what screws everyone up.
- zeroq 11mo ago
  fun fact: there's a guy with similar background to mine, with similar dedication to color, yet way more productive and he came out with this incredible piece of art: rebelle app As with most recent technological breakthroughs it uses math from 1931 paper to magically blend colors in ways that seems so realistic it's almost uncanny.
- dahart 11mo ago
  > It's definitely not something you can plug into a three-value model. What do you mean? And what is screwed up? We use 3 dimensions because most of us are trichromats, and because (un-coincidentally) most digital display devices have 3 primaries. The three-value models definitely are sufficient for many color tasks & goals. Three-value models work so well that outside of science and graphics research it’s hard to find good reasons to need more, especially for art & design work. It’d be more interesting to identify cases where a 3d color model or color space doesn’t work… what cases are you thinking of? 3D cone response is neither physical (spectral) color nor perceptual (“brain”) color, and it lands much closer to the physically-based side of things, but completely physically justifies using 3D models without needing to understand the brain or perception, does it not?
  - IgorPartola 11mo ago
    I had experimented with some photo printing services and came across one professional level service that offered pigment inkjet printing (vs much more common dye inkjet printing). Their printers had 12 colors of ink vs the traditional 4. I did some test photos and visually they looked stunning.
    - wongarsu 11mo ago
      "You only need three colors" is a bit of a cheat, because it doesn't really work out in reality. You can use three colors to get a good color gamut (as your screen is doing right now), but to represent close to every color we can see you would need to choose a red and blue close to the edge of what we can perceive, which would make it very dim. And because human vision is weird you would need some negative red as well, which doesn't really exist. Printing instead uses colors that are in the range we can perceive well, and whenever you want a color that is beyond what a combination of the chosen CMYK tones can represent you just add more colors to widen your gamut. Also printed media arguably prints more information than just color (e.g. "metal" colors with different reflectivity, or "neon" colors that convert UV to visible light to appear unnaturally bright)
      - 11mo ago

meodai 11mo ago

thanks for brining that up. Its a fight I stoped fighting a long time ago...

globular-toast 11mo ago

Is this why there appears to be a quite distinct plane inside the cube? If we were looking at them in the colour space would it look more uniformly spread?

adrian_b 11mo ago

While you are right, sometimes "RGB" is used as an abbreviation for some color space that is understood from the context, e.g. the CIE 1931 RGB color space (from which the CIE XYZ color space has been derived) or the RGB decoded correspondent of some TV color space, e.g. NTSC, PAL or SECAM.

virtualritz 11mo ago
I would really like to understand where that "sometimes" is, nowadays. RGB just means that color is expressed as a triplet of specific wavelengths. But what is red? And what does red = 1.0 mean w/o context (aka primaries & whitepoint)? What about HDR? What does green = 2.0 convey? Etc. For context, I worked in VFX production from the 90's to the early 2010's. About 25 years. And in commercially available VFX-related software, until the early 2000's, mostly, RGB meant non-linear sRGB, unfortunately (or actually: "whatever" would be more true). And it shows. We have VGX composed in non-linear color space with blown-out, oversaturated colors in highlights, fringes from resulting alpha blending errors, etc. A good compositor can compensate for some of these issues but only so far. If the maths are wrong, stuff will look shitty to some extend. Or as people in VFX say: "I have comments." After that, SIGGRAPH courses etc. ensured people were developing an understanding on how much this matters. And after that we had color spaces and learned to do everything in linear. And never looked back. Games, as always, caught up a decade after. But they, too, did, eventually.