Questions for Using DisplayCAL for Resolve

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  • #36717

    carloscfrias
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    Hi everyone,

    I recently adquired the Calibrite Colorchecker Display Plus mainly for color grading. I use the GUI color viewer in my 2017 iMac Pro.

    So, as I’m fairly new to all of this, I have a few questions that I hope some of you can help mi with:

    -If I’ve calibrated my  screen using DisplayCAL, why should I also make a lut for the color viewer? I’ve checked and the GUI color viewer changes when you change the icc profile in the computer so it should be already showing accurate colors, right? I only can think of the case in which I’ve set the display to a certain gamma and the video I’m grading is in some other.

    – As I’ve understood, the icc profile doesn’t limit the display to any color gamut in particular, just profiles what the display is capable of. So, how do I know if my display is correctly decoding the signal? My displays covers roughly the DCI-P3 gamut, should I have a DCI-P3 to BT.709  monitor lut every time I’m grading video for broadcast?

    I know these may be silly questions but I’m starting to get into the color management world and it’s a bit overwhelming, so any help is much appreciated.

    Thank you!

    #36765

    Vincent
    Participant
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    Hi everyone,

    I recently adquired the Calibrite Colorchecker Display Plus mainly for color grading. I use the GUI color viewer in my 2017 iMac Pro.

    So, as I’m fairly new to all of this, I have a few questions that I hope some of you can help mi with:

    -If I’ve calibrated my  screen using DisplayCAL, why should I also make a lut for the color viewer? I’ve checked and the GUI color viewer changes when you change the icc profile in the computer so it should be already showing accurate colors, right? I only can think of the case in which I’ve set the display to a certain gamma and the video I’m grading is in some other.

    Because due to MacOS color management limitations your display can only be described with an idealized matrix profile that may not account for 3D colospace volume irregularities (that an XYZLUT profile may capture)
    Of course if display is well behaved it can be described with such idealized profile. Validate profile using measurement report and you’ll see if your display can be accuraterly described by just 3 primatries and a idealized neutral TRC. If it’s fine then you may not need a LUT3D at all.

    – As I’ve understood, the icc profile doesn’t limit the display to any color gamut in particular, just profiles what the display is capable of. So, how do I know if my display is correctly decoding the signal? My displays covers roughly the DCI-P3 gamut, should I have a DCI-P3 to BT.709  monitor lut every time I’m grading video for broadcast?

    Load a sample videos with RGBCMY 100% saturation and see if they look sRGB/Rec709. You can measure tehm too with ArgyllCMS commandline “spotread”
    (“spotread -X my_colorimeter_correction.ccss”). Same with a set of IRE 0-100 for gamma.

    AVSforum had a set or MP4 for these task or to test a TV video embeded decoder.

    I know these may be silly questions but I’m starting to get into the color management world and it’s a bit overwhelming, so any help is much appreciated.

    Thank you!

    • This reply was modified 2 weeks, 4 days ago by Vincent.
    #36791

    carloscfrias
    Participant
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    Hi! Thank you very much for your answers.

    I ran Measurement Report using the BT.709 simulation profile and through the GUI viewer and the report was great. So, now I know I can trust the color accuracy when grading for BT709 but when I used the DCI-P3 simulation profile It was completely off and I don’t understand why if the profile showed that the display can cover that gamut. Any idea why?

    Thanks

    #36794

    Vincent
    Participant
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    Because content was not P3.

    #36797

    carloscfrias
    Participant
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    The measurement report was done using a P3 simulation profile through the GUI viewer on a Resolve project set to P3, what am I missing?

    #36798

    Vincent
    Participant
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    Who knows? you show no data.

    #36959

    carloscfrias
    Participant
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    You’re totally right, sorry.

    So, attached are the measurement reports using the BT.709 simulation profile with BT.1886 transfer function and P3 simulation profile with the same transfer function.

    In “Device link profile” it says I’m using a lut but I’m actually not using it, just the icc profile created with those same settings, because when setting the icc as device link profile it didn’t let me set a simulation profile.

    I guess this is where I got it wrong, but I still don’t understand why the BT.709 sim report is great and the DCI not and how can I switch between grading content for one gamut or the other and be sure I’m seeing accurate colors. I’m sorry, I’m very new to all of this.

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    #36962

    Vincent
    Participant
    • Offline

    In “Device link profile” it says I’m using a lut but I’m actually not using it, just the icc profile created with those same settings, because when setting the icc as device link profile it didn’t let me set a simulation profile.

    I guess this is where I got it wrong,

    Yes, and you are using it… in this verification, so do not use it for this task (P3 verification).

    but I still don’t understand why the BT.709 sim report is great and the DCI not and how can I switch between grading content for one gamut or the other and be sure I’m seeing accurate colors. I’m sorry, I’m very new to all of this.

    Because you are saying to Displaycal that it needs to reeencode patches through device link (= LUT3D). You are configuring DisplayCAL to reencode its color patches so display is showing Rec709 patches, as intended, and then you are configuring displaycal to compare those patches with P3, hence the error.
    Look at CIE a*b* plot.

    • This reply was modified 1 week, 2 days ago by Vincent.
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