Thursday, July 23, 2020
5:00pm - 6:00pm Pacific Time (UTC-12:00am Friday)
Please join us for the next meeting of this virtual working group (VWG). Future meeting dates for this month include:
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About the discussion of hue lines (Munsell vs others):
When comparing the research of hue lines, we need to consider the adaptation state: Munsell used a stable (I believe D50) chromatic adaptation and is focused on large scale equidistance (if this is a word).
Other experiments use other adaptation states and other methods of determining equidistance (JNDs or concatenated matching tests).
They cannot be compared directly.
Also quoting Fairchild from an email group discussion:
" … it is generally recognized that scales of color appearance
(large interval changes in attributes) do not linearly relate to small
interval changes near, and slightly above, threshold changes in
If you fit for JNDs it won’t agree with other metrics and vice versa.
I don’t think that the gaussian spectral distribution series should guide us, especially outside the confidence zone. And inside the confidence zone, they are not terribly bent, besides the red corner. And the red corner shows that the gaussian approach might have flaws.
Also, you would neglect the existence of colour constancy, which straights those lines anyway.
Cusp in the primaries (hexagonal mode):
I believe, the cusp in the primary is caused by the fact that in the primary hues both non-max components are equal, so no middle-component scaling is happening.
I also think that no natural system would be able to perform the hexagonal model. This might explain why we might prefer the initial version visually.
You should not forget that lots of cameras produce negative (all three channels) values when underexposed, because of the questionable practice of lens cap black subtraction.
We could add a recommended practice to correctly set the flare before applying gamut compression.
While the classical ~450nm range within sRGB / BT.709 shows skew, it is also worth examining ~612nm. Although it can be argued this is small fish compared to the impact of discrete, per-channel lookups.