- From: Chris Lilley via GitHub <sysbot+gh@w3.org>
- Date: Wed, 03 Mar 2021 22:27:58 +0000
- To: public-css-archive@w3.org
> I do rely a bit on R.W.G. Hunt's The Reproduction of Colour where he says: Hunts' work is well regarded and was seminal in it's day, but the first edition dates to 1957. The fifth edition, which I have, is from 1995 and is a somewhat light re-warming of the 1987 fourth edition. So in terms of evaluating the impact of the 1976 color models, it necessarily misses a lot of later work. > "This quantity is called the CIE 1976 (Luv*) colour difference Yes, it has a color difference formula. Comparative studies tend to rate it last, and more modern studies don't even evaluate it at all. > This type of space is useful in studies of colour television because, in the associated chromaticity diagrams I mentioned the (limited) value of chromaticity diagrams as one use case. For stage lighting design, in particular, they were fairly useful This was in the days before personal computers or even programmable calculators, it was a benefit to plot light sources on a large chromaticity diagram drawn on graph paper, connect them with a straight line, and be able to directly read off the resulting mixture chromaticities to two or perhaps three decimal places. Nowadays they are typically used in reviews or monitors or TVs, as a first approximation to show the gamut of one device compared to another. But due to the lack of perceptual uniformity it is easy to be led astray here. The MacAdam ellipses are still very elliptical and vary greatly in size. > LUV is near the bottom of the bunch for general purpose appearance modeling and reflective colors, Also for emissive colors. The flaws of the model are not suddenly cured because the light from a colored patch is directly generated rather than being the modified, reflected light. And there is only a small difference in geometry separating an opaque patch illuminated from above, and a translucent filter illuminated from behind by a backlight, as in LCD displays. > " HIGH DYNAMIC RANGE IMAGING (2010)" (I don't have that one yet, it is eye-wateringly expensive and I fund all my book purchases; W3C doesn't cover them.) > CalMAN™ uses CIELuv No, CalMan used to use Lab, with deltaE2000 for all color differences, and now has [moved to using ICtCp, with deltaITP](https://kb.portrait.com/help/ictcp-color-difference-metric). > I am not trying to dismiss LAB in any way, but I did add LUV to the models I'm working with, and I've found several aspects that make it favorable over LAB on self illuminated displays. Thanks for the clarification. Some of your comments, and in particular the personal mails you sent to me earlier, gave a very different impression where you seemed to suggest that any use of Lab was entirely erroneous and purely due to commercial pressure from one or two companies. I'm glad to hear you state more clearly your position - thanks! > I AGREE that Jzazbz is better. It is better in some ways. I find that the dreaded blue-to-purple shift in Lab is a little over-compensated, giving a turquoise case to blue chroma reduction. It also depends more on the state of adaptation and is sensitive to the scaling (where media white is placed, on the absolute luminance scale used in PQ). Lastly, while this is interesting and useful discussion, it is entirely unrelated to the topic of this particular issue "Don't force non-legacy colors to interpolate in a gamma-encoded space". I do hope, though, that your more wide-ranging views will be brought to bear during the [Color Workshop](https://www.w3.org/Graphics/Color/Workshop/). I would also encourage you to submit your research to a Color Science journal. -- GitHub Notification of comment by svgeesus Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/5883#issuecomment-790118061 using your GitHub account -- Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config
Received on Wednesday, 3 March 2021 22:28:00 UTC