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According to CIE 1931 color space chart, the sRGB gamut is what's inside the triangle:

enter image description here

As you can see from the diagram, blue is shown outside the sRGB gamut (at about 460 nm wavelength). Knowing that the monitor I'm currently using is pretty cheap (and it probably doesn't even support the full sRGB gamut, let along anything beyond it), how is it possible for me to see it? Is this diagram shifted somehow? If so, where can I get the "real" chromaticity diagram?

  • Typical computer monitors will have a larger gamut than sRGB. Also the chromaticity diagram that applies to your own vision may be 3 dimensional instead of 2 dimensional: bbc.com/future/story/20140905-the-women-with-super-human-vision. What may then happen is that in your 3 dimensional color space, the output of the monitor may be tilted while most other people will only see the two dimensional projection where the domain of the chromaticities is restricted to e.g. sRGB, this will then only appear to be stretched out at the boundary as mattdm points out. – Count Iblis Dec 9 '14 at 22:23
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    "Typical computer monitors will have a larger gamut than sRGB." I don't think that's the case, at least not for typical meanings of "typical". – mattdm Dec 10 '14 at 0:20
  • I don't think that's the case, at least not for typical meanings of "typical". A lot displays actually have larger gamut than sRGB / Rec. 709, this is especially true with Rec. 2020 colourspace becoming standard (Rec. 2020 largely encompasses sRGB / Rec. 709). – Kel Solaar Aug 8 '15 at 7:37
  • @KelSolaar We're getting there. But those displays are still not "typical" — there's just a handful being made and they're all expensive, high-end products. – mattdm Aug 8 '15 at 12:37
  • @mattdm Yes in regard to Rec. 2020, but pretty much all LCD / OLED displays nowadays have a larger gamut than sRGB, this is fairly easy to achieve as the primaries spds are much sharper than the ones from CRTs. – Kel Solaar Aug 8 '15 at 21:57
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The colors on the diagram are just meant to give you an idea of the color space. You could say that the sRGB space is "shifted" to be larger in order to create the illustration.

  • You mean, the sRGB triangle was drawn smaller? Or the entire chromaticity diagram was drawn smaller? – user1032613 Dec 9 '14 at 21:13
  • I mean that the sRGB colors are "stretched" out of the triangle they actually belong in. – mattdm Dec 9 '14 at 21:14
  • The colors on the diagram are just meant to give you an idea of the color space. This is not exact, depending the colourspace used to generate the diagram, you can entirely represent the colours of the chromaticity diagram. ACES2065-1 is such a colourspace, see my answer. – Kel Solaar Aug 8 '15 at 7:50
  • @KelSolaar It's hardly relevant that a colorspace which cannot be shown on any actual display exists. I stand by this answer as completely correct in the real world. – mattdm Aug 8 '15 at 10:12
  • @mattdm I'm not sure to understand what you mean? Are you implying that a colourspace that cannot be displayed does not exist? – Kel Solaar Aug 8 '15 at 11:11
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This is just a visualisation. The colours in the diagram do not represent the real colours of the noted wavelengths (what you see is dependent on the capabilities and calibration of your monitor anyway), but are chosen to give you an idea where the different colours rougly lie.

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Completely independent of the colors that are put inside the chromaticity diagram, no monitor (and no printer either) based on three visible colors can ever display all the colors the diagram represents. The reason is simply: Visible colors have to be inside the "horseshoe", and whatever three (or even six) colors you choose, the polygon defined by these colors can never fill the whole horseshoe. (All colors that can be created by a device are inside the polygon that is defined by the device's primary colors)

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It is probably complicated to reply accurately to your question without knowing which parameters have been used to generate the chromaticity diagram. However the following facts remain:

  • Your linked chromaticity diagram colours have been altered / blurred to attenuate the discontinuities introduced by conversion from CIE XYZ tristimulus values to sRGB / Rec. 709 colourspace.
  • The represented RGB colourspace triangle is actually not sRGB colourspace but CIE RGB colourspace which is entirely different.
  • If you were to depict accurately sRGB / Rec. 709 colourspace and use it to generate the chromaticity diagram colours, all the colours outside the triangle would not be represented accurately and would have one or more negative component(s) needing to be normalised and clipped in order to be displayed which is the reason you see them in your linked diagram.
  • It is entirely possible to represent the colours of the chromaticity diagram using a wide gamut colourspace such as ACES2065-1, they would not be displayed correctly though because no display exists that can represent such a colourspace.

Here is a normalised and clipped chromaticity diagram for sRGB / Rec. 709 colourspace, rendered in sRGB colourspace:

sRGB / Rec. 709

The same as above but this time not normalised but clipped:

sRGB / Rec. 709 - Unaltered

And one representing the ACES encodings for reference:

ACES Encodings

  • Would the downvoter mind explaining what's wrong with my answer instead of just downvoting without any proper explanations. Considering the OP question is partially incorrect, I did provided relevant points. – Kel Solaar Aug 8 '15 at 21:49
  • I think you are entirely misunderstanding the question. There's no question that some colorspaces exist which encompass the entire color space chromaticity diagram. The question is: given that the diagram itself is actually shown in sRGB (or smaller!) on the original asker's monitor, why are there colors visible outside of that triangle? – mattdm Aug 9 '15 at 0:54
  • I think you are entirely misinterpreting my answer :) I understood the question(s) properly (because there are actually multiple questions) and replied to them on each of my points, by first introducing the fact that the diagram has altered colours (so they are wrong), second correcting the fact it is not sRGB being represented, third stating the reason why you can see the colours (because they are clipped and altered), fourth (bonus) giving an alternative colourspace that can represent entirely the visible spectrum, fifth I provided an accurate chromaticity diagram. – Kel Solaar Aug 9 '15 at 2:54
  • I agree, Kel, In particular this point "The represented RGB colourspace triangle is actually not sRGB colourspace but CIE RGB colourspace which is entirely different' is correct. Describing the triangle as representing sRGB is simply wrong. – doug May 26 at 4:32

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