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Wasn't the point that yellow was a poor choice of colour to add since there is not much missing from the gamut between the red and green primaries? I'm no exper

Wasn't the point that yellow was a poor choice of colour to add since there is not much missing from the gamut between the red and green primaries? I'm no expert, but looking at the diagram I'd say a cyan colour would be far more gamut expanding.

dedward 16y ago
Your eyes are sensitive to those areas in different amounts - while it looks like there is a lot more space to expand towards cyan - you probably wouldn't notice it as much as the extra R+G pop you're going to get with the added yellow.
teilo 16y ago
The edge of the blob on that chart represents the color that can be achieved by mixing the three chosen primaries. If you wanted to expand the curve outward along the top edge of the blob, you need yellow pixels with a more intense color than can be produced by mixing red and green. What this will achieve is not just brighter yellows. The whole curve expands upward, leading to more intense colors along that entire portion of the gamut.
- Robin_Message 16y ago
  No, the triangle is what can be achieved by mixing the primaries. The blob is what the eye can distinguish between. I think the blob is the http://en.wikipedia.org/wiki/CIELUV_color_space http://en.wikipedia.org/wiki/CIELUV_color_space but I'm not certain. Can I suggest we look at http://en.wikipedia.org/wiki/CIE_1931_color_space#Definition_of_the_CIE_XYZ_color_space http://en.wikipedia.org/wiki/CIE_1931_color_space#Definition... instead? There you can see that three primaries cover a large range of human colour perception. In particular yellow is well covered, but there is a big gap around cyan, hence my earlier comment that a cyan primary would seem more useful. This corresponds to the requirement for a negative red colour to reach between 440nm and 540nm. Note red is the only primary that goes significantly negative. Also since we expect television to be displayed using three RGBish primaries, the triangle is also the only colours that are actually transmitted in any TV signal or recording. Now, it is possible that the small gain in yellow is noticeable, and leads to a nice visual "pop" when viewing the screen, but it really isn't gaining you a lot. I'd be more interested in a cyan primary (think of the skies!) or an HDR screen with a real range of brightnesses.

dedward 16y ago

Your eyes are sensitive to those areas in different amounts - while it looks like there is a lot more space to expand towards cyan - you probably wouldn't notice it as much as the extra R+G pop you're going to get with the added yellow.

teilo 16y ago

The edge of the blob on that chart represents the color that can be achieved by mixing the three chosen primaries. If you wanted to expand the curve outward along the top edge of the blob, you need yellow pixels with a more intense color than can be produced by mixing red and green. What this will achieve is not just brighter yellows. The whole curve expands upward, leading to more intense colors along that entire portion of the gamut.

Robin_Message 16y ago
No, the triangle is what can be achieved by mixing the primaries. The blob is what the eye can distinguish between. I think the blob is the http://en.wikipedia.org/wiki/CIELUV_color_space http://en.wikipedia.org/wiki/CIELUV_color_space but I'm not certain. Can I suggest we look at http://en.wikipedia.org/wiki/CIE_1931_color_space#Definition_of_the_CIE_XYZ_color_space http://en.wikipedia.org/wiki/CIE_1931_color_space#Definition... instead? There you can see that three primaries cover a large range of human colour perception. In particular yellow is well covered, but there is a big gap around cyan, hence my earlier comment that a cyan primary would seem more useful. This corresponds to the requirement for a negative red colour to reach between 440nm and 540nm. Note red is the only primary that goes significantly negative. Also since we expect television to be displayed using three RGBish primaries, the triangle is also the only colours that are actually transmitted in any TV signal or recording. Now, it is possible that the small gain in yellow is noticeable, and leads to a nice visual "pop" when viewing the screen, but it really isn't gaining you a lot. I'd be more interested in a cyan primary (think of the skies!) or an HDR screen with a real range of brightnesses.