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Author Topic: Color Managment Expectations  (Read 5652 times)

Scott Martin

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Color Managment Expectations
« Reply #20 on: July 15, 2010, 08:55:15 PM »

Quote from: fike
Where should I start?

Calibration and color management with ICC profiles are two different processes that must come together for optimal results. In this case you've made a good profile but haven't calibrated the device for the lighting you were shooting in. You might say we "calibrate" cameras by selecting the optimal exposure and white balance for every lighting situation we work with. In this case, the image appears to be underexposed and the white balance is too cool. This topic can get very deep, especially when we start talking about making prints that match the original objects, but I think that the jist of what you're looking for.

fike

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Color Managment Expectations
« Reply #21 on: July 16, 2010, 12:41:55 PM »

Quote from: Onsight
Calibration and color management with ICC profiles are two different processes that must come together for optimal results. In this case you've made a good profile but haven't calibrated the device for the lighting you were shooting in. You might say we "calibrate" cameras by selecting the optimal exposure and white balance for every lighting situation we work with. In this case, the image appears to be underexposed and the white balance is too cool. This topic can get very deep, especially when we start talking about making prints that match the original objects, but I think that the jist of what you're looking for.

I think you are missing what has occurred.  I photographed a known standard target.  I tried calibrating to that target and got poor results.  Cliff used different software, working on my JPG, and got results that were subjectively-speaking much closer.  I am not looking for a primer on color management. I am looking for ideas on what could have gone wrong with the Passport color checker software.
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Scott Martin

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Color Managment Expectations
« Reply #22 on: July 16, 2010, 11:57:20 PM »

Quote from: fike
I tried calibrating to that target and got poor results....  I am looking for ideas on what could have gone wrong with the Passport color checker software.
I'm quite familiar with the process. You didn't calibrate, you've *profiled* the process and implemented it *without calibration* (proper exposure and white balance). Proper exposure and white balance are what's missing.

fike

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« Reply #23 on: July 17, 2010, 08:48:21 AM »

Quote from: Onsight
I'm quite familiar with the process. You didn't calibrate, you've *profiled* the process and implemented it *without calibration* (proper exposure and white balance). Proper exposure and white balance are what's missing.
Then how did Cliff  (Crames) get such good results?  I thought that the purpose of the color checker was to help me set the white balance and make a good profile for a unique lighting condition.
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Scott Martin

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« Reply #24 on: July 17, 2010, 12:35:24 PM »

Quote from: fike
Then how did Cliff  (Crames) get such good results?
He's applied color corrections to compensate for the lack of proper white balance and exposure. It's kinda like taking a poor film scan and making it look good. These days we can avoid color correction by setting our white balance and exposure correctly with digital cameras.

Quote from: fike
I thought that the purpose of the color checker was to help me set the white balance and make a good profile for a unique lighting condition.
Yes, the white balance of the image you attached, however, wasn't set correctly and neither was the exposure. That's were you need to focus your efforts - white balance and exposure.

crames

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Color Managment Expectations
« Reply #25 on: July 17, 2010, 01:42:03 PM »

Quote from: fike
Then how did Cliff  (Crames) get such good results?  I thought that the purpose of the color checker was to help me set the white balance and make a good profile for a unique lighting condition.

The inCamera software that I used generates an ICC profile from the ColorChecker that corrects not only hues and chromas, but also makes automatic changes that affect the tone curves and white balance. It forces all of the patches to match target values exactly in lightness, chroma, and hue. Other colors in the scene then fall into place.

I think the difference is that dng profiles don't adjust the lightness/contrast or white balance. You set those manually, and then the camera profile gets the various hues and chromas in line. As far as I know, it doesn't matter if you use the ColorChecker Passport-generated profile, or create one with the Adobe DNG profile editor, it's the way camera profiles work.

Like Onsight said, to use a dng camera profile in ACR, not only do you assign the custom camera profile, but you also have to click a neutral patch for white balance, and adjust exposure to a reasonable setting (for example set exposure so that the lightest gray patch has a green channel of 143 if your target working space is AdobeRGB). Set all of the other setting like "recovery", "fill light", "blacks", "brightness", etc. to zero. This will get you closer to getting the target values of the patches on the Color Checker and other colors in the scene.

Cliff
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natas

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« Reply #26 on: July 17, 2010, 09:49:47 PM »

Did you set the white balance using the neutral gray on the color checker? Make sure you select the correct one
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fike

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« Reply #27 on: July 18, 2010, 07:47:11 AM »

Quote from: natas
Did you set the white balance using the neutral gray on the color checker? Make sure you select the correct one

I think that is probably the major root of my problem.  I expected the color-checker profiling software would have done that for me. I haven't had a chance to get back to them, but I'll do that when I have some time for learning and experimentation.
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Scott Martin

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« Reply #28 on: July 18, 2010, 12:27:27 PM »

Yes I think you find that things will fall into place when the white balance and exposure are set correctly. Start by clicking on the Passport's white patch with the white balance tool and adjust the Exposure to achieve the values that math that of a CC reference file. Afterwards, work on achieving the ideal exposure in camera so as to minimize development steps. These are your *calibration* steps that will compliment the *profile* that you've generated. Again, calibration and profiling are two different processes that work together.

JeffKohn

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« Reply #29 on: July 18, 2010, 03:43:54 PM »

Quote from: fike
I think that is probably the major root of my problem.  I expected the color-checker profiling software would have done that for me. I haven't had a chance to get back to them, but I'll do that when I have some time for learning and experimentation.
The DNG profiles are not meant to correct for white balance, if they did they would only be useful for that specific color temperature (and even then only when you wanted a neutral WB, which for creative reasons is not always the case). So when applying your profile to an image you still need to set the appropriate WB setting in raw converter (which should be easy in your case since you can just use the eye dropper on one of the neutral patches in the CC checker, generally the second lightest patch is considered the best bet).

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