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alanterra
alanterra
Inspiring
August 29, 2020
Answered

Generate and apply camera profile to a TIFF with a Color Checker Passport in the image?

  • August 29, 2020
  • 3 replies
  • 2870 views

Someone sent me a jpg with a color checker passport in the image. I want to use that to improve the color fidelity of the image. I think I understand most of this process, but I can't quite get it to work.

 

To remind you about using a Color Checker Passport for digital photography (correct me if I am wrong here), you do the following:

  • take an image under standard lighting that includes a color checker passport, being careful to save the file as a raw or dng file (let's not discuss biluminant profiles!)
  • use the color checker plugin to save a profile for your camera. The profile is saved in ~/Library/Application Support/Adobe/CameraRaw/CameraProfiles/
  • Then, after you restart Lightroom, you can apply this profile to any photo that was made with this exact camera (go to Profile: Browse in the develop module to find the profile)
  • But, Lightroom is careful to only allow you to apply profiles from the SAME camera, and doesn't show you profiles from DIFFERENT cameras (which makes sense).

 

Now I have a TIFF (in sRGB space) that has a Color Checker Passport in the image. I tried the following

  • export the TIFF (from Lightroom Classic) as a dng
  • use the color checker software (I used the desktop version) to make a ".dcp" profile for that image
  • but now that profile does not show up when you go to Profile: Browse in the Develop module, probably because the camera ID doesn't match between the dng in step one and the camera profile in step two

 

I think (hope) that if I can just get Lightroom Classic to recognize that this Camera Profile "belongs to" this image, I could apply it and, hopefully, get better color fidelity for the image. Any thoughts about how to do this? I suspect it is just some metadata in the dng file and/or the dcp file that I need to massage and make consistent, but I'm not sure how to figure this out.

This topic has been closed for replies.
Correct answer D Fosse

This was first posted in the Photoshop forum (slightly differently phrased and with example color checker images).

https://community.adobe.com/t5/photoshop/use-colorchecker-to-improve-color-in-jpg-tiff/td-p/11395519?page=1 

 

I don't think camera profiles is a particularly useful approach here, I think this is better adressed by looking at the tone response curve. That should get you to the target more easily and more conveniently. So I'm reposting my reply from the PS forum, see original example image at bottom here:

 

--------

 

The difference here is the tone response curve. Your top example has slightly exaggerated contrast, a curve that is a little too steep, and the bottom example slightly reduced contrast, a curve that is a little too flat. More contrast = higher saturation.

 

The colors themselves seem to be basically OK.

 

Each patch in a standard colorchecker has standardized Lab values. Here they are. Note the six neutral patches and the L values:

 

But here's the tricky part: you can't reproduce the tone curve to these numbers in the file and expect a good result in print. Paper color and maximum ink impose their own limits, reducing the available contrast range and compressing the target. So you have to compensate. How much depends on the print process, but for an average process I'd say your top example is about right. The bottom example is too drab. It'll look flat and dull.

 

The Lab numbers can be translated to any color space you happen to be working in - even Lightroom % numbers. My working starting point for a flat, evenly lit subject is usually to fix the #4 gray patch to 48 % in Lightroom, the white patch to 96%, and the darkest patch to somewhere between 8 and 15% depending.

 

Don't underestimate the importance of the black point. It is responsible for most of the perceived visual "punch". Set the black point very carefully, and you usually need to decide on a case by case basis.

 

And BTW here's the OP's original example referred to above:

 

3 replies

JP Hess
JP Hess
Inspiring
August 29, 2020

You indicated that you tried to export a tiff image as a DNG. That really won't work because it's kind of like trying to un-cook an egg. You cannot create a raw file that way. Raw image data must be generated by a device that can create raw image data.

alanterra
alanterraAuthor
Inspiring
August 29, 2020

I think you are right, JimHess, but in fact Lightroom Classic does allow you to uncook this egg. It seems that whatever the uncooked egg is, it isn't useful for making omelettes. 

JohanElzenga
Community Expert
JohanElzengaCommunity Expert
Community Expert
August 29, 2020

No, Lightroom does not allow you to uncook the egg. Many people think that a DNG file is a raw file, but it is not. DNG is just a wrapper. It can indeed contain raw data and then it's a raw file, but it can also contain RGB data and then it is not. Lightroom allows you to wrap RGB data in a DNG wrapper, but that is not the same as uncooking the egg.

-- Johan W. Elzenga
    JohanElzenga
    Community Expert
    JohanElzengaCommunity Expert
    Community Expert
    August 29, 2020

    The .dcp profiles that ColorChecker Passport creates are raw profiles. I don't think you can create such a profile for RGB files and I am quite surprised that ColorChecker Passport even let you do this. Even though you converted the tiff file to dng, it was still an RGB file and so ColorChecker Passport should have rejected it. 

    -- Johan W. Elzenga
      D Fosse
      Community Expert
      D FosseCommunity ExpertCorrect answer
      Community Expert
      August 29, 2020

      This was first posted in the Photoshop forum (slightly differently phrased and with example color checker images).

      https://community.adobe.com/t5/photoshop/use-colorchecker-to-improve-color-in-jpg-tiff/td-p/11395519?page=1 

       

      I don't think camera profiles is a particularly useful approach here, I think this is better adressed by looking at the tone response curve. That should get you to the target more easily and more conveniently. So I'm reposting my reply from the PS forum, see original example image at bottom here:

       

      --------

       

      The difference here is the tone response curve. Your top example has slightly exaggerated contrast, a curve that is a little too steep, and the bottom example slightly reduced contrast, a curve that is a little too flat. More contrast = higher saturation.

       

      The colors themselves seem to be basically OK.

       

      Each patch in a standard colorchecker has standardized Lab values. Here they are. Note the six neutral patches and the L values:

       

      But here's the tricky part: you can't reproduce the tone curve to these numbers in the file and expect a good result in print. Paper color and maximum ink impose their own limits, reducing the available contrast range and compressing the target. So you have to compensate. How much depends on the print process, but for an average process I'd say your top example is about right. The bottom example is too drab. It'll look flat and dull.

       

      The Lab numbers can be translated to any color space you happen to be working in - even Lightroom % numbers. My working starting point for a flat, evenly lit subject is usually to fix the #4 gray patch to 48 % in Lightroom, the white patch to 96%, and the darkest patch to somewhere between 8 and 15% depending.

       

      Don't underestimate the importance of the black point. It is responsible for most of the perceived visual "punch". Set the black point very carefully, and you usually need to decide on a case by case basis.

       

      And BTW here's the OP's original example referred to above:

       

      alanterra
      alanterraAuthor
      Inspiring
      August 29, 2020

      I tried to move this post to this forum because I didn't phrase the original post in the Photoshop forum in a way that was giving me useful answers (I thought). I didn't want to edit the post after posting, and I couldn't remove it, and, as I said, there is something in Photo Raw + Photoshop that is confusing me, and trying to address my confusion and my question at the same time would be hopeless.

       

      D_Fosse gave substantially the same answer in the other forum, and I think it is certainly the best way to proceed. Thank you, D_Fosse.

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