Ed -
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 chromaticity
<https://en.wikipedia.org/wiki/Chromaticity>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?
I'm not sure how this new work isn't something like a re-affirmation or
reformulation of the MacAdams work
<https://en.wikipedia.org/wiki/MacAdam_ellipse> you reference, although
the Just Noticeable Difference ellipses really just reference the
local-metric of the CIE space they are registered on?
I haven't followed up on Anil's '82 JOSA paper but would like to...
My deepest dive into this space, especially related to
color-compression, was the Faber-White-Saltzman work
<https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/5130701>
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).
On 3/5/23 11:21 AM, Angel Edward wrote:
Steve,
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.
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.
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.
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.
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).
Ed
__________
Ed Angel
Founding Director, Art, Research, Technology and Science Laboratory
(ARTS Lab)
Professor Emeritus of Computer Science, University of New Mexico
1017 Sierra Pinon
Santa Fe, NM 87501
505-984-0136 (home)edward.an...@gmail.com
505-453-4944 (cell) http://www.cs.unm.edu/~angel
On Mar 4, 2023, at 4:22 PM, Steve Smith <sasm...@swcp.com> wrote:
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:
The general topic is the non-Reimannian nature of perceptual color
spaces.
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).
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 tSNE
<https://en.wikipedia.org/wiki/T-distributed_stochastic_neighbor_embedding><https://en.wikipedia.org/wiki/T-distributed_stochastic_neighbor_embedding>which
prefers a locally accurate metric over a global one.
The LANL work on this non-Reimannian color space:
https://www.pnas.org/doi/full/10.1073/pnas.2119753119
A popular article about that work:
https://www.fastcompany.com/90780869/it-could-take-20-more-years-for-scientists-to-truly-understand-color
<https://www.fastcompany.com/90780869/it-could-take-20-more-years-for-scientists-to-truly-understand-color>
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?
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