Talk:MacAdam ellipse
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[edit] Metric Spaces
I reverted to the previous version, but I think the new rewrite pointed out some weaknesses in the previous version.
- I don't think introducing the XYZ Euclidean metric is helpful. Such a metric is never used in color analysis any more than some weird metric is used in measuring distances in 3-space. Yes, we can define some weird metric in 3-space, but there is a "natural" metric - the Euclidean metric. In the same way, the natural metric for color space is the perceptual one estimated by MacAdam, and others. I realize that a Euclidean metric is implicitly used when talking about the fact that the MacAdam ellipses are in fact ellipses and not circles, but I don't think the idea should be given such formal recognition.
- Speaking of formality, I think the highly mathematical explanation is good, but should be preceeded by a plain English version, in the flavor of the restored version (but more precise).
If you don't want to attempt a rewrite, I will soon give it a try. PAR 03:10, 17 August 2005 (UTC)
I chaged a few words to be mathematical precise, but generally agree with the rest. --Ylai 23:21, 17 August 2005 (UTC)
- For those with no background in metric topology, the section about metric spaces is still not going to make any sense. I think instead it would be useful to show a picture of what these ellipses look like in a less-distorted (w.r.t. MacAdam metric) color space, and give some descriptive indication of the type of transformation between the two, with or without some math to go along with that. In general, it seems a lot of the technical math-y parts of the color articles in Wikipedia don't have a good written explanation of what the math means. I realize this is not an easy job, but it would be very valuable, as most of those looking up color spaces are unlikely to have an undergraduate level math background. --jacobolus (t) 07:25, 28 October 2006 (UTC)
[edit] CIE ab space
There is a sentence in the article which reads:
The CIE ab space with the natural metric d, defined by MacAdam's measurements gives a metric space that is homeomorphic to the CIE xy space with d' and in this space the MacAdam ellipses become circles.
I have never heard of the "CIE ab space" (nor the CIE xy space for that matter) and I would like to delete this sentence unless someone can explain it to me. PAR 11:06, 21 February 2007 (UTC)
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- If thats the case, it does not transform MacAdam ellipses to perfect circles. It comes close, but is not exact. I will delete the sentence, or modify it. PAR 05:04, 22 February 2007 (UTC)
[edit] Ellipse or bean
Was the research by MacAdam doen for all colors or only the colors in a section of CIExy color space (with Y=50)? If it was for all colors would it then not be more likely that the ellipses / circles (2D) would be beans/spheres (3D)? BartYgor 13:13, 15 July 2007 (UTC)
- MacAdam's original research was for a fixed luminance of about 48 cd/m^2. Brown and MacAdam subsequently investigated the effects of varying luminance, and developed what are known as "Brown-MacAdam ellipsoids" which specify discrimination along the luminance axis as well. They found that the projection of these ellipsoids onto chromaticity space were fairly constant in size from 3 to 30 cd/m^2. Wyszecki and Fielder also measured discrimination ellipsoids under somewhat different conditions. For an excellent discussion of all of these points, see chapter 5.4 of "Color Science, 2nd Edition" by Wyszecki and Stiles. PAR 14:21, 15 July 2007 (UTC)
