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: Mon, 03 Jun 2013 15:44:07 -0700
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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