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Thread: Converting from Device Camera Profile to a standard RGB Color Space

  1. #1
    Member Ale_Paris is on a distinguished road
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    Converting from Device Camera Profile to a standard RGB Color Space

    Following the other topic...

    What I am trying to do is to use the ICC Profile to change the appeareance of my images.
    To do so I've created a base ICC profile in combination with my camera (for certain lights condition) and I've started to play around with it in Profile Editor to tweak the colors of the images themselves.

    I know it's not the classical way of using the ICC profiles but I've seen that the results I obtain are of a better quality rather than making the color corrections with the classical panels in photoshop.
    I also like the fact that I can apply the profiles to the images while I am shooting and see directly the results (and if to apply some modifications).

    I know I should better use some "abstract ICC Profile" but I am going crazy as I don't understand how to create them and how to use them...
    So I am directly editing the original device camera profile but I am going crazy to convert the images back a RGB space (like Adobe 1998 or ProPhoto) as the colors change.

    What I have been doing so far is this:
    - Rendering the image from RAW to TIFF with all the parameters set to 0.
    - Assing the modified ICC Profile.
    - Converting the image to LAB color space with Absolute Colometric rendering mode.
    - Converting the image to Adobe RGB with Relative Colometric rendering mode.

    This method works perfectly for some of the profiles I've generated (it removes posterization if there is some) but terribly for other (as it changes the colors, especially in the shadows).

    If anybody has any suggestion I would really appreciate because this problem is driving me crazy.

    Thank you!


    Ale

  2. #2
    Banned rx61 is on a distinguished road
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    Re: Converting from Device Camera Profile to a standard RGB Color Space

    Hi Ale,

    i might be able to help - but a couple of questions first:

    - have you calibrated your monitor?

    - where are your images going to end up - print or screen?

    Best,
    Anna

  3. #3
    Member Ale_Paris is on a distinguished road
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    Hello Anna,

    thank you for getting back to me.

    Yes, my monitor is calibrated.
    The pictures are going to be both printed and showed on screen.

    Thank you very much!


    Ale

  4. #4
    Donor Gargoyle will become famous soon enough
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    Some questions:

    What is your objective? Why the need to tweak the camera color profile that you have already custom created? How was your camera profile created e.g. test targets use, light conditions, profiling software and settings?

  5. #5
    Member Ale_Paris is on a distinguished road
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    Hello,

    sorry for the late reply.

    My objective is to create a series of different ICC profiles that already contains some color corrections so that, loading these profile in Capture , I can directly see how the image will look like after the color corrections.
    I want to make different profiles that contains different "effects".

    I know I can create some *.ICM profile directly in capture but, from what I've understood, creating a specific *.ICC profile and making the corrections in that , leads to better results. For example we could consider when, to increase the exposition of an image, we can change the gamma of a profile rather that playing with "curves" or "exposure" tabs in Photoshop.

    I think I may also use some abstract profiles to do the same thing but, as I can't understand how to create them, what I am doing is:
    - Shooting an IT8 target with my camera (I know there are some better target like the SG but this is what I have)
    - Coverting the RAW in TIFF in Capture with all the parameters set to 0.
    - Loading the resulting image in either Monaco EZ Color or Profile Maker to create the basic profile.
    - Opening the "basic profile" just created in Profile Editor to make all the color corrections.

    What I really really like of Profile Editor is the fact that it enables me to select color based on Chroma, Luminance and Hue, and to shift them. And you can't do this directly in Capture or, using DNG Profiles, in Adobe DNG Profile Editor.

    If anybody knows a method to create a abstract profile that contains just the color shift, curve corrections and so on, it would be my dream.

    Thank you very much!


    Ale

  6. #6
    Banned rx61 is on a distinguished road
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    hi ale,

    hmm ok i am understanding a little more of what you are trying to do. it does seem like a very complicated workflow though - if you are shooting raw, why don't you use lightroom to create a number of custom presets for your camera in different lighting conditions? this would be the easiest and least destructive way to play around with hue, luminance and so on. since you are converting to tif format currently, you are definitely losing some information at some point (you told me that you are using the images for both print and web - so a profile conversion will need to be applied somewhere).
    I can understand you like having the profiles in camera for the preview - however i personally would never rely on the in-camera preview to make final decisions about editing.

  7. #7
    Member Ale_Paris is on a distinguished road
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    Hello rx61,

    thank you for getting back to me.

    I know there are easier way to get to similar results but I prefer ICC profiles for a series of reasons:
    1) by changing the profile you can reach a "better quality" color correction if compared to the classical panels in photoshop or similar applications. For example, to recover an underexposed image, of the best way I know, it's using profiles.
    2) the color corrections I need to do often involve shifting colors in a well defined range (hue, chroma, luminance) that would be otherwise impossible (if not extremely difficult) in photoshop, capture , lightroom, etc. Imagine that I need to shift the skin colors to make them lighter but at the same time I want to have my saturated and fairly dark red even more saturated and dark. With DNG profile, or ICM profile made in Capture , it's only possible to select Hue and Chroma but not Luminance and therefore, this correction would be impossible.

    What I would love to make is a series of profiles, let's say that recreate a certain type of film, another film, polaroid, cross processing and then, once I've selected the profile, I would adjust the "real-life" scene to make it perfect to work with the profile.

    It would be amazing if I would be able to generate an abstract profile that contains only the color modifications (and not also the modifications made by, let's say, Profile Editor, to create the original camera profile in first instance) so that I could apply it to different cameras without problems (to certain extent...).

    Any small suggestion might help! Thank you!


    Ale

  8. #8
    Donor Gargoyle will become famous soon enough
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    I find your objectives above too far away to what is attainable and the workflow seems a bit mess-up. Foremost the IT8 test target which I assume to be an IT8.7/2 reflective? This is for scanners not digital camera unless you are shooting or replicating photographic prints. Its color gamut is too small for your camera for real life scenes so also are its spectral reflectances.

    Unlike scanner profile the purpose of the camera profile is not on high color accuracy. You cannot do this to tristimulus RGB camera unless the subjects you are shooting are trichromatic such as your monitor display, photographic prints etc.

    Your issues here is about creating a good camera profile which you can satisfactorily edit the colors with your photo applications without creating too much artifacts. The camera profile has a huge color gamut that need to be perceptually mapped to your display profile, working profile and output profiles. Perceptually I mean it has to be smooth and even throughout the gamut. This all depend on the quality of your camera targets and your profiling software. The IT8.7/2 is not right target for that. Afterwards you can edit the colors in LAB mode in your photo applications which is same as Abstract profiles. This is the current workflow. For state of art you may research ciecam2002 color appearance models. I am wondering what profiling and photo applications allow transforming back and forth from this color models for color editing?

  9. #9
    Member Ale_Paris is on a distinguished road
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    Hello Gargoyle,

    thank you for your contribute.

    Yes, the target is an IT8/2 reflective that came together with a scanner I use to scan my images shot on film.
    I know it's not the best target I could use but the alternative was a 24ColorChecker from X-rite. Unfortunately the SG chart from X-rite costs over 300€ and I can't afford it at the moment.

    Your issues here is about creating a good camera profile which you can satisfactorily edit the colors with your photo applications without creating too much artifacts. The camera profile has a huge color gamut that need to be perceptually mapped to your display profile, working profile and output profiles. Perceptually I mean it has to be smooth and even throughout the gamut.
    Yes, this is my main concern at the moment.
    I am aware that I am not using a correct "procedure" to obtain what I want but somehow it seems to be working. The only problem I have is when it comes to coverting from the camera profile I've custom created (with all the color corrections) to a standard profile like Adobe 1998 or ProPhoto as colors slightly change and I get some artifacts.
    It has to be noticed that, sometimes, I also get the opposite effect: I apply an extreme custom profile (with exaggerated color tweaks) that posterize very badly when applied in Photoshop. I then convert to LAB mode and back to Adobe 1998 or ProPhoto and the banding disappears leaving the color transactions very smooth.

    Going back to creating the general profile (the without all the color modifications) in first istance what you've pointed out is exactly the reason why I would love to work with "abstract profile" rather then "camera profile".
    If I could create a profile that comprehends only the color corrections I want rather than also containing all the information created when generating the original profile with Profile Editor or EZ Color in combination with the chart shot with my camera I think I would resolve part of the issues I am experiencing.
    Rather than generating a "camera profile" and then applying all the modifications to this profile, thus generating a secondary camera profile with the color corrections applied, isn't it possible to start the process with a kind of "empy profile" to which apply all the modifications and generating an abstract profile?

    I tried to research "ciecam2002 color appearance models" but I could find only super technical books and I did not really understand how could I use them.
    I am sorry but I am new to this and I get confused easily!

    THANK YOU!

  10. #10
    Donor Gargoyle will become famous soon enough
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    Hi Ale_Paris,

    To answer your second paragraph on artefacts I think it has something to do with gamut mapping issues. If you check your camera profile gamut in ProfileEditor it must have a much larger gamut than your monitor profile. Mapping it to a smaller gamut such as AdobeRGB then to even smaller gamut of your monitor profile using the colorimetric intent method in Photoshop will clip the colors and posterize the saturated parts of your image. The solution is to use the Desaturate Monitor Color options in Color Settings and also avoid converting your camera profile to smaller gamut like AdobeRGB unless you are using ICC version 4 profiles with Perceptual Reference Medium Gamut.

    I'm not sure about your statement that converting to Lab mode then to AdobeRGB or ProPhotoRGB resolved the posterizations. Its unlikely or just coincidental on that particular image. Please check the gamut size of your camera profile.

    Abstract profile is theoretically possible but what software are you going to use? Photoshop Replace Color features is somehow I think similar to the ProfileEditor Selective Color. I'm not sure if ProfileEditor is better because I think they work on the same Lab colorspace unless its CIECAM02 color space. The solution is either above or replace your monitor with a with gamut as big as your camera profile if using Photoshop.
    Last edited by Gargoyle; 12-22-2012 at 04:13 AM.

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  12. #11
    Member Ale_Paris is on a distinguished road
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    Hello Gargoyle,

    thank you for coming back to me.

    I've checked the modified camera profile and the monitor profile that I've created with i1ProfilerD2Lidition with ColorThinkPro 3.0 and these are the results:
    • Modified Camera Profile Gamut Volume --> 232.655
    • Monitor Profile Gamut Volume --> 512.211

    Also, graphing the modified camera profile, it's cleary much much smaller than a normal Adobe RGB 1998. It really surprises me that it posterizes so much!

    In Color Settings how much do you think I should desaturate colors?
    thing that I did not get is if then I'll see the actual colors of the image or simply everything more desaturared but smoother? I guess it's the second option...

    Finally, I have to say that I am working on a MacBook Air at the moment and it doesn't surprise me if the monitor quality is not exceptional. :-)

    How can I find out if Profile Editor works with CIECAM02 color space?
    Are there any preferences to check?

    -------------------------------------------

    Yesterday I've also tried another road: creating a LUT in Adobe SpeedGrade, exporting it, and then loading it in Photoshop with a Adjustment Layer.
    The thing is that I always get different colors from what I see in SpeedGrade and, depending on the LUT I load (when you export your "look" in Speedgrade it automatically saves different LUTs in different formats) I get completely different colors!

    Then I've found a way (still have to try) to embedd the LUT in an ICC Profile:
    [URL="http://opencolorio.org/userguide/baking_luts.html"]http://opencolorio.org/userguide/baking_luts.html[/URL]

    THANK YOU VERY MUCH!

  13. #12
    Donor Gargoyle will become famous soon enough
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    Hi Ale_Paris,

    Checking my own results the device gamut volume of ProfileMaker own IT8ExampleScan.tif is 1,205,580. My monitor is 876,661 while AdobeRGB is 1,207,520, and ProPhoto is 2,548,220. The primary colors of IT8ExampleScan.tif in scanner RGB are: cyan 9,48,114, magenta 79,8,63, yellow: 187,135,1, black 5,4,10, red 73,11,15, green 10,37,13, blue 4,4,39, white 236,230,224. Scanner RGB values outside the gamut of the IT8 target were extrapolated.

    IMO it seems small for your modified camera profile. Did you check your unmodified camera profile for posterizations as well as its gamut volume? Did you check whether the posterization occured outside the IT8 target RGB values? Try the Universal SmoothnessTest.tif file there at http://colormanagement.org/en/testimages.html Assign your camera profile both modified and unmodified, monitor profile, sRGB, ProPhoto, AdobeRGB in Photoshop, experiment with Desaturate Monitor Colors and conversions maybe that will pinpoint the problem.

    How much to desaturate depends on your monitor gamut. In my case around 40% for ProPhoto. It changes the actual colors of your image but allows you to see those out of gamut colors.

    Corrections for the ciecam02.... During profile creation especially perceptual gamut mapping perhaps ciecam02 and other color apperance models were used internally however the ICC profile PCS is Lab or XYZ colorspace.

    I cannot comment on that Adobe SpeedGrade but I think its better to check the color values itself using Colorpicker tools than the colors seen from your monitor.

  14. #13
    Member Ale_Paris is on a distinguished road
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    Hello Gargoyle,

    I'm sorry for the late reply but there have been the Christmas vacation in the meantime and I wanted to perform some tests as you suggested.

    I've tried to calibrate my monitor once again but I had some problems (I'm opening a new topic about it) so I keep using the older monitor profile.

    I've created my monitor profile with i1ProfilerD2Lidition and the I've analyzed it with ColorThinkPro.
    Where do you find the RGB primaries values?
    I don't really get what you mean when you say: "Scanner RGB values outside the gamut of the IT8 target were extrapolated."

    The un-modified camera profile I've originally created as a gamut volume of 2.609.160.
    The modified camera profile I was referring to before was highly desaturated for having a kind of sepia-effect. That's probably the reason for the small gamut volume?

    thing that I don't understand is why, if I apply a small gamut volume profile, the image posterizes. Shouldn't it be the contrary? For example when you apply ProPhoto to a picture that is 8bit.

    I'm playing around with the image you gave me but, so far, applying the various profiles, it doesn't posterize.

    But I'm wondering now...
    When you create a custom ICC Profil for you camera (without making some strange tweaks as I am doing) what is the standard way to convert it to Adobe 1998 or ProPhoto, in order to leave you colors as they are (obviously to certain degrees...)?

    Thank you very much!


    Ale

  15. #14
    Junior Member Iuri Bernardi is on a distinguished road
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    Quote Originally Posted by Ale_Paris View Post
    Hello Gargoyle,

    I'm sorry for the late reply but there have been the Christmas vacation in the meantime and I wanted to perform some tests as you suggested.

    I've tried to calibrate my monitor once again but I had some problems (I'm opening a new topic about it) so I keep using the older monitor profile.

    I've created my monitor profile with i1ProfilerD2Lidition and the I've analyzed it with ColorThinkPro.
    Where do you find the RGB primaries values?
    I don't really get what you mean when you say: "Scanner RGB values outside the gamut of the IT8 target were extrapolated."

    The un-modified camera profile I've originally created as a gamut volume of 2.609.160.
    The modified camera profile I was referring to before was highly desaturated for having a kind of sepia-effect. That's probably the reason for the small gamut volume?

    thing that I don't understand is why, if I apply a small gamut volume profile, the image posterizes. Shouldn't it be the contrary? For example when you apply ProPhoto to a picture that is 8bit.

    I'm playing around with the image you gave me but, so far, applying the various profiles, it doesn't posterize.

    But I'm wondering now...
    When you create a custom ICC Profil for you camera (without making some strange tweaks as I am doing) what is the standard way to convert it to Adobe 1998 or ProPhoto, in order to leave you colors as they are (obviously to certain degrees...)?

    Thank you very much!


    Ale
    Can you send a screen-shot from Colorthink about your profile?

  16. #15
    Member Ale_Paris is on a distinguished road
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    Sure!

    Here are the print screens from ColorThinkPro regarding the un-modified camera profile.

    Thank you!

    [URL="http://postimage.org/image/3mb57k84b/"]http://postimage.org/image/3mb57k84b/[/URL]
    [URL="http://postimage.org/image/bkp832k5h/"]http://postimage.org/image/bkp832k5h/[/URL]
    [URL="http://postimage.org/image/adfvoljet/"]http://postimage.org/image/adfvoljet/[/URL]
    [URL="http://postimage.org/image/ltmammxl1/"]http://postimage.org/image/ltmammxl1/[/URL]

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