Custom Camera Profiling: A Look at the QPcard 203 book

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Ernst Dinkla:
>>Ernst, what would you rely on then?<<

In landscape photography etc; the camera manufacturer's estimations of sensor responses + a Babelcolor improved PTFE grey-white tablet or similar white tablet gadgets that include black traps. For Cityscapes the same + the Color Checker Passport, though one wonders what light reflected from walls do in that case.
http://www.babelcolor.com/main_level/White_Target.htm

For me me as an amateur, some stacked plumbers's Teflon tape discs used as a white tablet if I approached it that serious.

For art reproductions; continuous spectral light around 5000K, the Babelcolor tablet, a Color Checker card. That is what I see the photographer do that does that work for me. Or improved cards with patches spectrally measured that suit the original, oil paint sample books, watercolor sample books. For Cruse scanners there is some work done like that. It works with a dedicated fluorescent light source though.

If the Cruse had two different fluorescent lights, two scan runs with one lamp each and the appropriate algorithms to discriminate what the metamerism effect then tells about the original color areas, it could be more selective. What is done in the cheap HP G4050-4010 desktop scanners. Poorman's multi-spectral scanning. Does not do a better job on the CMY dyes used in photography where all desktop scanners are calibrated on but does a better job on for example a reflective original painted with acrylics. See third PDF at this page:
http://www.image-engineering.de/index.php?option=com_content&view=article&id=57&Itemid=91
That is making use of "metamerism" metameric failure to nail colors.

Your approach is more or less the opposite, you think the metameric match of two colors in one light source to your eyes, the green patch of the Color Checker card and foliage green, should be equally matched to the camera in one light source if you calibrated the camera with the CC card in that light. It does not have to be like that though due to the different ways a green color is created in nature and due to a difference between your eyes and the sensor responses. It would be improved if you had a Color Checker card that is made of foliage itself, stone samples, bark cuts and if possible a sample that recreated what makes the sky blue. Not an easy road if we count all the optical effects:
http://en.wikipedia.org/wiki/Optical_phenomenon

--
Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
December 2012, 500+ inkjet media white spectral plots.

samueljohnchia:
Quote from: Ernst Dinkla on February 21, 2013, 06:18:07 AM

In landscape photography etc; the camera manufacturer's estimations of sensor responses


Ernst, I use Adobe Camera Raw as my default raw converter, not Canon DPP for my 5D Mark II. Adobe does not use the camera manufacturer's estimations of sensor responses but measures their own. Despite their exotic hardware and software I find that their rendering of color is both quantifiably less accurate, and also visually than custom profiles that I make for my camera.

Yes, I want to expect that a metameric mismatch (I referred to this as color relationships) of two colored objects I see under daylight to be reproduced as accurately by the camera+raw converter as possible, unless metamerism issues lie with the sensor itself, not being able to discriminate between the two colored objects. I agree that the limited material of a small patch target is never going to be able to describe a broad range of natural and artificial surfaces, matter and non-matter substances. What other hope can individuals like me have to approach an increasingly elusive ideal color rendering of my digital images?

Are custom profiles a waste of time, money and effort? Can I not hope to get better results than the generic offerings from Adobe/OEM?

Is the improvements that I am seeing illusions?

mac_paolo:
Newest version (1.20) of Qpcalibration fixed the issue I had for the profiles that were not showing under Lightroom.

Ernst Dinkla:
Quote from: samueljohnchia on February 21, 2013, 09:29:19 AM


Is the improvements that I am seeing illusions?


Let me say:
1 Sheer luck if the color in the scene is created without colorants like dyes or pigments.
2 A happy result if the color in the scene was created by colorants like dyes and pigments but not the ones used in the CC and/or OP card.
3 As could be expected if the colors are based on the same pigments used in the card.
4 Any mix of the above.

Your samples do not represent all colors of nature, the dice have to roll more often.

The reasoning that the CC card has a color constancy in the patches that resembles the color constancy of colorants in nature and does not need to represent all colors in nature is an approach that I find dubious. The patches are non fluorescent, nature does not have that precaution, it does not cut UV, it does not suppress fluorescence. Color can be created additive in stippled color patterns or as subtractive transparent  layers and in many more ways that interfere with sensor resolutions. Light reflects on flower petals and it goes through flower petals. Texture does its thing like on butterfly wings. The sensors mimic human color perception but both humans and sensors deviate from the average aimed at. There are way more conditions that are not present in a card with say 12 pigments for 30-140 mixed patches that reflect light. It is an art building on traditions in color film making to create sensors + sensor filters + RAW output + RAW development that is not easily improved with a calibration on that last step.

There is another thing. You might create a good representation of the scene in whatever way and when printed you think you can improve upon that result. Within the boundaries of what looks natural. Would you object? Is the original scene still around and do you want a 1:1 reproduction of the scene or the most pleasent picture that still looks natural and would pass any critical eye without objection? The print will not be nature, it will not have the dynamic range of nature, it is made with 6 pigment hues at most. You will adapt that print that it does give the impression and the impact of the scene which is not a true reproduction of the scene. And when you make a reproduction of art, with far more conditions in control, in the end there still is that small part where another reality has to be created as the match is never 1:1. I have made reproductions that were 1:1, the original has to be damned close to an inkjet print to make that possible.

Like in the other thread is written, there is not a DeltaE stick to measure with but the result has to appeal to you and possibly more people.

--
Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
December 2012, 500+ inkjet media white spectral plots.

samueljohnchia:
Just a quick update; I am too busy to conduct the other camera profiling testing yet.

I received my replacement QPcard today. While the card is in much better condition than the previous one, it still exhibits scuff marks - see attached picture. Interestingly, tests with sunlight hitting the target at various angles - even angles that produce the worst glare on the scratches - resulted in almost similar profiles. Anyhow I would rather not have scuffed patches to begin with.

Another thing that I mentioned previously, that the QP generates profiles that are greener than the CC+DNG PE. I now know why. The gray patches in the QPcard are redder than the CC, both measurably and visibly. The QP software must be basing the color mapping after white balancing off one of the lighter gray patches, and that is skewing the profile towards green. If ones wishes to test a QP profile against a DNG PE profile, different WB values must be used for each profile.

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