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<p>Ed -</p>
<p>Great contribution. Despite having lived in and around all of
this from transmissive to reflective to emmissive CG hardware as
well as cameras I have felt that some of the issues brought up in
the paper were things that have long been swept under the carpet.
I noticed the business you mentioned about having evaluated only
luminance and *implying* that this might/could/should apply across
<a moz-do-not-send="true"
href="https://en.wikipedia.org/wiki/Chromaticity">chromaticity </a>variations
as well is tantamount to pulling many of the issues out from under
the carpet then deliberately sweeping many of them right back
under it? <br>
</p>
<p>I'm not sure how this new work isn't something like a
re-affirmation or reformulation of the <a moz-do-not-send="true"
href="https://en.wikipedia.org/wiki/MacAdam_ellipse">MacAdams
work</a> you reference, although the Just Noticeable Difference
ellipses really just reference the local-metric of the CIE space
they are registered on?</p>
<p>I haven't followed up on Anil's '82 JOSA paper but would like
to...</p>
<p>My deepest dive into this space, especially related to
color-compression, was the <a moz-do-not-send="true"
href="https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/5130701">Faber-White-Saltzman
work</a> on color quantization in the early 90s? My application
was related to trying to exploit frame-to-frame quantization to
(better) extend the limited NTSC color gamuts implied by video
recording of the era (vs the 64M color space we were getting on
our 16mm film recorders of the time).</p>
<p align="center"><img moz-do-not-send="true"
src="https://webcube-general.s3.amazonaws.com/eizo/media/contentassets/2014/10/27/01_6.jpg"
alt="" width="655" height="634"><br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 3/5/23 11:21 AM, Angel Edward wrote:<br>
</div>
<blockquote type="cite"
cite="mid:DE8D9FFA-2E7F-47A5-8CD2-3B206902E7C4@gmail.com">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
Steve,
<div class=""><br class="">
</div>
<div class="">Thanks for the post. I haven’t been following the
research in color for a long time although it remains one of the
areas I love to talk about in my books and lectures. </div>
<div class=""><br class="">
</div>
<div class="">The paper is really interesting although I’m not
sure how the result could be used in areas such as compression
since both small and large differences in color are important.
Maybe on the user side but not on the transmission or storage
side. The Fast Company article shows a superficial understanding
of color spaces at times and thus exaggerates the potential
results of the research.</div>
<div class=""><br class="">
</div>
<div class="">I have a couple of potential issues with the paper
that I thought would have been brought up by reviewers. Early
the paper, there is statement that seems to say that RGB is what
the cones in our eyes sense. Perhaps it's just a poorly stated
sentence but the there types of cones do not measure r, G and B
in a 1 to 1 way. The three types have peaks in the Green,
between Green and Yellow, and in the Blue. In addition, we less
than 10% of cones are blue sensitive (and these tend to be on
the periphery of the retina). The standard NTSC RGB system was
based on the available technology and not on perception.
Luminance (L in Lab, Y in XYZ) is mostly Green and Yellow. What
makes things more complex is that we are more sensitive to
small changes in color (MacAdams ellipsoids of Just Noticeable
Differences) in the blue and least sensitive in the Green. </div>
<div class=""><br class="">
</div>
<div class="">I would have not pointed out the above except that I
was worried that the experiment was done totally on luminance,
changing L* with a*=b*=0. I would have found the paper more
convincing if the measure was applied to changes in chromaticity
in the experiment.</div>
<div class=""><br class="">
</div>
<div class="">We used to worry about these issues way back in the
70’s when I was working with my friend Anil Jain at the USC
Image Processing Institute. One problem then finding color maps
for compressing a color image form 3 bytes/pixel to 1 byte/pixel
and for pseudo coloring grayscale images. The problem was to
find a map that in which each step was perceptually equal. Anil
did a paper that appeared in the JOSA in 82 using geodesics in a
perceptual color space. The problem with the result was that the
colors he got were really ugly compared to the usual thermal map
using cool colors (blues and greens) going to hot colors
(yellows and reds).</div>
<div class=""><br class="">
</div>
<div class="">Ed</div>
<div class="">__________
<div class="">
<div><br class="">
Ed Angel<br class="">
<br class="">
Founding Director, Art, Research, Technology and Science
Laboratory (ARTS Lab)<br class="">
Professor Emeritus of Computer Science, University of New
Mexico<br class="">
<br class="">
1017 Sierra Pinon<br class="">
Santa Fe, NM 87501<br class="">
505-984-0136 (home)<span class="Apple-tab-span" style="white-space: pre;"> </span> <span class="Apple-tab-span" style="white-space: pre;"> </span><a
href="mailto:edward.angel@gmail.com"
class="moz-txt-link-freetext" moz-do-not-send="true">edward.angel@gmail.com</a><br
class="">
505-453-4944 (cell) <span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span><a class="moz-txt-link-freetext" href="http://www.cs.unm.edu/~angel">http://www.cs.unm.edu/~angel</a><br
class="">
</div>
</div>
<div><br class="">
<blockquote type="cite" class="">
<div class="">On Mar 4, 2023, at 4:22 PM, Steve Smith <<a
href="mailto:sasmyth@swcp.com"
class="moz-txt-link-freetext" moz-do-not-send="true">sasmyth@swcp.com</a>>
wrote:</div>
<br class="Apple-interchange-newline">
<div class="">
<meta http-equiv="content-type" content="text/html;
charset=UTF-8" class="">
<div class="">
<p class="">This may or may not relate to the current
threads about mind v body, perceptual nature of
reality, etc that we have been flogging, but it is a
topic I lived in and around for most of my career and
found it both familiar/compelling and a little
disturbing:</p>
<p class="">The general topic is the non-Reimannian
nature of perceptual color spaces.</p>
<p class="">The broadly accepted non-Euclidean color
spaces described by the CIE formulations (1931 and
1976) has been widely accepted while the RGB/CMYK/HSV
Euclidean approximations are what most folks use for
pretty good practical reasons (particular the
conveniences of tristimulus/process color
specification and synthesis).<br class="">
</p>
<p class="">This recent (1 year old) publication work by
some LANL folks was shoved in my face/space recently
(as a correlate to the problems we have been working
with on trying to understand the underlying space of
abstract high dimensional (very non-linear) problems
such as ensemble steering/exploration in the World3
model. Our favored method (of the moment) is a
variant of <a moz-do-not-send="true"
href="https://en.wikipedia.org/wiki/T-distributed_stochastic_neighbor_embedding"
class="">tSNE</a><a moz-do-not-send="true"
href="https://en.wikipedia.org/wiki/T-distributed_stochastic_neighbor_embedding"
class=""> </a>which prefers a locally accurate
metric over a global one.<br class="">
</p>
<p class="">The LANL work on this non-Reimannian color
space:<br class="">
</p>
<blockquote class="">
<p class=""><a moz-do-not-send="true"
href="https://www.pnas.org/doi/full/10.1073/pnas.2119753119"
class="moz-txt-link-freetext">https://www.pnas.org/doi/full/10.1073/pnas.2119753119</a></p>
</blockquote>
<p class="">A popular article about that work:<br
class="">
</p>
<blockquote class="">
<p class=""><a moz-do-not-send="true"
href="https://www.fastcompany.com/90780869/it-could-take-20-more-years-for-scientists-to-truly-understand-color"
class="">https://www.fastcompany.com/90780869/it-could-take-20-more-years-for-scientists-to-truly-understand-color<br
class="">
</a></p>
</blockquote>
<p class="">I'm guessing this (at least) crossed Ed
Angel's awareness, perhaps there are a few others here
who care about this level of detail/abstraction on
color/perceptual spaces? Frank is probably a lot more
up on the nuances of (non) Reimannian manifolds than I
ever will be... I don't know if this represents an
interesting example of the utility of such?<br
class="">
</p>
</div>
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