Camera calibration workflow

[geotzo]

I have been asked to do some very demanding copy work for wooden surfaces that will go on a catalogue. The client wants absolute color control and I m not really sure which way to go. Up to now I have used the 24 patch GMcbeth card (full size), for the first shot of the setup, then run the odd script in Photoshop, use the final values and that's it. Though most copies turn out fine after that, some of them don't look very near to the real thing in terms of color, contrast etc. Is there anything more accurate I could do? Is that your workflow when doing copy work? Some times the results are a bit dull in color. Forgot to mention my lighting is very stable (using profoto generator) as I ve measured its values to differ not more than 60K between shots.
Thanks for any help

[smthopr]

I have been asked to do some very demanding copy work for wooden surfaces that will go on a catalogue. The client wants absolute color control and I m not really sure which way to go. Up to now I have used the 24 patch GMcbeth card (full size), for the first shot of the setup, then run the odd script in Photoshop, use the final values and that's it. Though most copies turn out fine after that, some of them don't look very near to the real thing in terms of color, contrast etc. Is there anything more accurate I could do? Is that your workflow when doing copy work? Some times the results are a bit dull in color. Forgot to mention my lighting is very stable (using profoto generator) as I ve measured its values to differ not more than 60K between shots.
Thanks for any help
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Your approach sounds quite reasonable to me. I suspect that even if you placed the Macbeth chart in the frame, you might come out to the same result.

Therefore, I might suggest that you are observing metamerism.  See the wiki at:[a href=\"http://en.wikipedia.org/wiki/Metamerism_(color)]metamerism link[/url]

Basically, the object that you're photographing may reflect color in a different way than the chips on the Macbeth chart.

Anyway, that's my best guess

[EricWHiss]

There are routines that let you weight the colors that are most important to the image - perhaps for your case the yellows and browns are most important?   Tindeman I think is the fellow that has the weighted routine and I know Tom Fors has one too that maybe now allows for a weighted or priority calibration.

I've actually not had much luck with these routines for my cameras - and use other raw converters.   Canon DPP seems to get you better color for canon files, flexcolor for my Leica DMR files, and C1 for nearly anything else. Raw Developer is good too.   Most of the programs besides ACR and Lightroom use camera profiles.  And some of them are quite good.

[geotzo]

Canon DPP seems to get you better color for canon files
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That's interesting to know, since I have been using Photoshop Raw and Lightroom for all my camera raw files, I never thought using Canon DPP for my 1ds Mkiii. Never bothered, but I guess I should.
The idea of metamerism never occurred to me because I thought it only takes place on paper printing, but then again you might be right.
Thanks

[BobDavid]

I think you are a good candidate for camera profiling. I profiled my medium format camera, which I use almost exlusively for copy work, with the X-Rite SG kit. It has made a huge difference in terms of color and luminance accuracy.

[Raoul]

You may want to create a camera profile based on the lighting at your client's. I built one based on an IT8.7/2 target using LPROF free software (http://lprof.sourceforge.net/). Easy and fast, average dE below 3 after calibration, compared to average dE higher than 10 using the camera manufacturer's profile.  

After the calibration I created a contrast curve to reflect correct tonality of the grey patches. The overall workflow gives nice results even with batch processing.

24 patches seem few to build a profile though. The IT8 has 264 patches + grey levels. Some targets have close to 1000 patches, but that may be overkill.

Total cost was about 10 EUR for the IT8 target, plus a lot of time reading about color management. Both time and money seem to be well spent. Probably a more expensive commercial solution will work better, but this approach got me at least in the ballpark.

[digitaldog]

First thing first. Select the Raw converter. Then you can decide if you're going to tweak the calibration (ala ACR and Lightroom) or try to build an ICC device profile.

[sojournerphoto]

First thing first. Select the Raw converter. Then you can decide if you're going to tweak the calibration (ala ACR and Lightroom) or try to build an ICC device profile.
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I calibrated my 5D in LR/ACR and have much improved results. I have a couple of presets for each iso, one aiming at a 'neutral' rendition and one at a more contrasty first try. Skin tones and reds/greens are much improved, but I suspect that for work where colour accuracy was critical there would be more to do!

Mike