Re: Colorimetric Accuracy in the Field
Re: Colorimetric Accuracy in the Field
- Subject: Re: Colorimetric Accuracy in the Field
- From: Stanley Smith <email@hidden>
- Date: Tue, 04 Jun 2013 15:48:56 -0700
Well, the obvious goal is dE2000 =0.0. -- a goal that is equally
obviously not attainable. Sure, we reproduce our paintings in books, on
displays at a press check, and projected on unpredictable machines for
lectures. I would gently suggest that given the truly bad color memory
we all have, that if the color presented on any of these platforms is
not "accurate" to the degree that everyone here seems to be striving
for, it won't make a damn bit of difference to the viewer. These
differences are really only noticeable when you compare the reproduction
with the original in a controlled setting, and I never see visitors to
the Getty walking around the gallery with the catalog open-- eyes
darting from the book to the painting (I'm somewhat embarrassed to note
that I do this all the time, and it is often a sobering experience). Of
course we need to be close, and we do strive for that, but we have no
control over the viewing conditions of a person leafing through one of
our catalogs-- a fact that renders extreme color accuracy standards
moot.
One more thing-- Just because curators strive for accuracy in
reproduction, it doesn't mean that publishing professionals always do.
I've told this story more than once: We had a big Paul Strand show a
few years back, and I did what I mentioned above-- walked around the
gallery with the book open. Strand printed very dark and flat-- he
loved the murky print. Our reproductions were shockingly different, but
looked much like other reproductions of his work that I had seen in the
past-- normal contrast and more open shadows. When I asked our
publisher why there was such a difference the answer was very revealing:
They couldn't sell any books if they had faithfully reproduced the
original prints-- it would have looked like a mistake. In Strand's
defense, I believe he was used to throwing a lot of light on a print
when evaluating-- not a lighting condition that is often reproduced by a
casual viewer.
Stanley Smith
J. Paul Getty Museum
Stanley Smith
Head of Collection Information and Access
J. Paul Getty Museum
1200 Getty Center Drive, Suite 1000
Los Angeles, CA 90049-1687
(310) 440-7286
>>> On 6/3/2013 at 04:24 PM, in message
<email@hidden>,
José Ángel Bueno García<email@hidden> wrote:
And with Nikon D90 get dE2000=1.67 with flash units without Pirex on a
ColorChecker. Where is your goal?. And your images from X-ray or UV,
where do you evaluate and compare?, isn't a display?. And when you go to
any kind of meeting or to publish your analysis and conclusions, don't
you print on paper?.
2013/6/3 José Ángel Bueno García <email@hidden>
I'm photographer. I do not art. Go out with your Sinar and your SG
ColorChecker.
2013/6/3 Stanley Smith <email@hidden>
Those of us in the museum world are very concerned with colormetric
accuracy, and go to great lengths to achieve this-- even to the point
of
developing multi-spectral capture methods (I worked recently with Roy
Berns and Sinar AG to develop a six-channel system that achieves
accuracy on a SG ColorChecker of less that 1 CIEDE2000). Our need for
this has little to do with how the image ends up looking on what ever
display or paper-- it is mostly useful in scientific painting
conservation analysis. I honestly cannot think of another situation
where this level of accuracy is useful or practical. It's like walking
towards a wall in intervals covering half the distance each time. Will
you ever get to the wall? No, but you'll be close enough.
Photographers don't care-- they goose the colors later anyway to
express
their interpretation of a scene-- this is not new-- Ansel burned and
dodged fiercely. Leave the science to the scientists. Go out and make
art.
Stanley Smith
Head of Collection Information and Access
J. Paul Getty Museum
1200 Getty Center Drive, Suite 1000
Los Angeles, CA 90049-1687
(310) 440-7286
>>> On 6/3/2013 at 02:49 PM, in message
<email@hidden>, Jeffrey Stevensen
<email@hidden> wrote:
I've been following this discussion and though it is geek-intriguing,
in which I include myself. And I'm still catching up. But it seems
completely irrelevant to being a working photographer in the field.
Mr.
Goren seems to be advocating, to use a reference to our earlier,
photo-chemical past, "the perfect film developer."
>
>> I'm sure I could have taken my i1 Pro into the field with me and
gotten spot measurements of everything in sight I could lay my hands
on
>
> Indeed, that's hard and a lot of work. But short of that, what proof
do we have? Isn't the goal of colorimetry an non ambiguous set of
color
measurements that don't rely on a personal interpretation of what we
see
as color?
>>
I've got to side with Mr. Rodney throughout. He asks for the
definition
of "colorimetric accuracy" and in reply gets assurances based on
memory.
If I stand on a beach at magic hour in golden light, is the goal a
capture of the subject in a perfect colorimetric rendering of that
moment's unique and beautiful light, which is what I take to be the
end
result of some in the "pro-colorimetric" side of this debate?
Certainly
not a capture of the subject that ignores the momentary unique
lighting
and says, this is what it would have looked like under some sort of
"standard" light; there would be no point to doing that except for
some
scientific goal with clearly stated conditions of measurement accuracy
and toolset accuracy.
I think I'm interested in reproducing my perception of what I see,
which is the object or scene in that unique lighting, and hopefully a
little extra personal poetry of imagination. Anything requiring
"matching" must state all the objectively-measured conditions and
definitions of what is a match. That masterful matching print of the
painting or museum piece will definitely include the specification for
the conditions of viewing, including lighting levels, lighting color
temperature, evenness, etc. to stay within the accepted deviation
constituting a "match." There is no such thing as the original and
copy
matching to some fine, objective numeric standard across all mediums
and
viewing conditions. And even if it did, Mr. Goren states
>>> Colorimetry is "the science and technology used to quantify and
describe physically the human color perception
>
Ah! We are back to human perception, "perceptual rendering"! Anybody
on
this list care to step up and claim to have perfect human "standard
observer" vision?
> in contrast, my workflow with Raw Photo Processor amounts to
shooting
a target, feeding that target to a Perl script that spits out white
balance and exposure numbers, doing a copy / paste of those (three)
numbers back into Raw Photo Processor, and applying those settings to
the shot of the artwork. That's the sum grand total of my
color-correcting workflow; everything else is either sharpening or
lens
geometry and peripheral illumination correction or panorama-type
stitching or cleaning up smudges on the original or the like.
So rendering the scene from raw as described, personal expression is
thus confined to… composition only? Choice of subject? Angle of view?
Perspective and lens choice? Just going to a momentary 2D rendering?
How
is this "accurate" to a changing, moving, scene-scanning, 4D
space-time
personal experience through one unique set of eyeballs?
> I output from RPP to a BetaRGB TIFF, do whatever needs to be done in
Photoshop without any color transformations, and then feed the BetaRGB
TIFF to Argyll for a gamut-mapped perceptual rendition to the printer
profile, and print the result.
We all want and usually get pretty close to making the print look
awfully "accurate" in an ICC-manged workflow with a variety of tools,
but this comes after rendering the raw file to where we like it, so no
argument there.
>
> I daresay getting comparable quality out of Adobe's rendering
engine,
if even possible, would require many, many hours of very intensive and
skilled post-processing.
To be science, one must specify all the conditions under which the
experiment is conducted, the single variable to be tested and how the
final result is then measured. Mr. Rodney is right that that has not
been provided, nor is what artists do, nor even generally what clients
hire photographers to do.
My sincere appreciation to all parties for a fascinating diversion,
but
now to make some money...
Jeff Stevensen Photography
82 Gilman Street
Portland, ME 04102
207-773-5175
207-807-6961 cell
http://www.jstevensen.com
blog http://photosightlines.com
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