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Just going to sound really pedantic here, but RGB does not capture the entire colour space. In fact, it only captures about 35% of the colours the human eye can
by toolslive 3mo ago
Just going to sound really pedantic here, but RGB does not capture the entire colour space. In fact, it only captures about 35% of the colours the human eye can perceive.
https://www.oceanopticsbook.info/view/photometry-and-visibility/from-xyz-to-rgb https://www.oceanopticsbook.info/view/photometry-and-visibil...
- piker 3mo agoOkay, but that was a really useful metaphor if incomplete in a lot of ways. It made me say “oh”.
- wtallis 3mo agoYou seem to be conflating "RGB" with one particular RGB color space: sRGB. That's a common enough conflation to make, but not appropriate when you're trying to be pedantic.
- toolslive 3mo agoDoesn't matter: there's no RGB model that captures the colour space. That exactly the reason CIE exists.
- interroboink 3mo agoSince you seem to know, and I am curious, doesn't CIE[1] effectively use RGB to describe its space, too? Eg: the r̅(λ) g̅(λ) b̅(λ) color matching functions? Or is there something else in CIE you're referring to? [1] https://en.wikipedia.org/wiki/CIE_1931_color_space https://en.wikipedia.org/wiki/CIE_1931_color_space
- toolslive 3mo ago[dead]
- adrian_b 3mo agoCIE (1931) is a RGB color space, based on monochromatic primary colors with wavelengths of 700 nm (red), 546.1 nm (green) and 435.8 nm (blue). However the entire color space of CIE RGB (1931) includes points where some of the RGB components are negative. Because positive components are sometimes desirable (e.g. because one can make light filters whose outputs are those components), the alternative XYZ representation is derived by computation from the original CIE RGB, which had been obtained from experiments with human subjects. Any RGB model can capture the entire color space, even sRGB. The limitation is not at capturing, but only at reproducing colors when using RGB emitters, because the emitters cannot reproduce components with negative values. There are no RGB models that can capture the entire color space without having points where some components are negative. This is caused mostly by defects of the human color vision, e.g. by the fact that the red receptors are also sensitive to violet light, not only to red light, and by the fact that the selectivity curves of the photoreceptors do not have ideal shapes.
- jacobolus 3mo agoYou can represent any arbitrary colors using RGB values for whatever "R", "G", and "B" primaries you like, they just might not fit in the range [0, 1]. (At least, under the strong assumptions we make in color modeling using the CIE system of colorimetry; the basic keyword is "Grassmann's laws".)
- klysm 3mo agoNot true, you can make the R G and B points far enough out to capture the entire human gamut
- inigyou 3mo agoYou can specify any colour if you can use values below 0 and above 100%.
- toolslive 3mo agohold on. Just realised it's not even (part of ) a vector space. It's not linear, non-euclidian and can't be mapped onto 3 dimensions. It's not even constant or always reproducible: Look at an object; Observe colour X; then look at the wrong thing; then look back and you might observe colour X' != X.
- esafak 3mo agoThis is solved through https://en.wikipedia.org/wiki/Primary_color#Imaginary_primaries https://en.wikipedia.org/wiki/Primary_color#Imaginary_primar... that sit outside the visible spectrum.
- Aardwolf 3mo agoThe eyes receptors are RGB too and they definitely capture all visible colors by definition (to be pedantic, yes there's also the rods for night vision, and the 'R' is more like yellow)
- toolslive 3mo agoTetrachromacy !?