How to create a custom test chart with 256 grayscale patches?

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  • #36344

    mat a
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    Hi

    On ledoge’s novideo_sRGB, he recommends creating a test chart with 256 grayscale patches (neutral).

    I have found the patch editor but I have no idea how to use it.

    Could anyone tell me how to use it to create a simple curve + matrix profile with 256 grayscale patches plus the other requisite patches?

    Thank you.

    #36349

    Raj S
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    In DisplayCAL, go to the Profiling tab, select one of the existing LUT testcharts, and then press “Edit Testchart” (the button that looks like 9 squares). It’ll open up a window where you can edit testcharts.

    Set “Neutral patches” to 256. (Grayscale patches)

    Set “Single channel patches” to 2. (RGB patches, I’d recommend 2 as a minimum)

    Set “Iterative patches” to 0. (Colour patches)

    Set “Multidimensional” to 0. (Mixed patches that are generated)

    Set “White patches” to 1 and “Black patches” to 1 (Optional, ensures you’ve got at least 1 white patch and 1 black patch)

    These settings will give you 256 grayscale patches + R, G, B.

    You can always play around with the settings. You can also look at the existing LUT profile testcharts and see what they do. Or select the existing ones and just set Neutral to 256 for a much better approach.

    • This reply was modified 1 month, 2 weeks ago by Raj S.
    #36356

    mat a
    Participant
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    Thank you Raj.

    Vincent and yourself have proved invaluable.

    #36389

    mat a
    Participant
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    Thank you.

    How do I load an existing chart? I want to use the normal simple curves + matrix one and just add 256 grey patches.

    Thank you!

    #36400

    Raj S
    Participant
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    Under Profiling > Testchart, select an existing testchart like “Extended testchart for LUT profiles”, press the editor button and set Neutral patches to 256.

    Then press “Create testchart”. Once that’s done you can press “Save as” and save it wherever you want. By default they’re stored in “C:\Program Files (x86)\DisplayCAL\ti1” so I just save them there. If it doesn’t let you then just save it somewhere else.

    Once it’s saved, it will ask you “Do you want to select this testchart?”. Press yes.

    #36401

    mat a
    Participant
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    Done.

    Thanks!

    #36799

    S Simeonov
    Participant
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    Should we use the first method or just add 256 neutral patches and leave everything at defaults?

    #36804

    Raj S
    Participant
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    I’d probably recommend the existing testchart method.

    The first method (new testchart) is just a bare minimum.

    The second method (existing testchart) will give a more accurate profiling of the display. Whether Novideo_sRGB will take full advantage of it is another question entirely. Someone will have to test it.

    But until then, it’s certainly not a bad thing to have a more accurate profile.

    #36821

    S Simeonov
    Participant
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    I’d probably recommend the existing testchart method.

    The first method (new testchart) is just a bare minimum.

    The second method (existing testchart) will give a more accurate profiling of the display. Whether Novideo_sRGB will take full advantage of it is another question entirely. Someone will have to test it.

    But until then, it’s certainly not a bad thing to have a more accurate profile.

    If I edit the large testchart for lut profiles, the patches are reaching above 770…

    #36822

    Raj S
    Participant
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    That’s because the Large LUT testchart profile has lots of “Multidimensional” patches. It’s unnecessary and a waste of time for Novideo_sRGB.

    You can safely decrease “Multidimensional” to as low as 3 if you’d like. That will generate at least one C, M, Y patch in the profile. I think 5 is the sweet spot. Going higher is unnecessary.

    I’d personally use:

    “Single channel” = 21, “Neutral” = 256, “Multidimensional” = 5

    [Optional] “Iterative” at 256 (for better accuracy, if also using the profile for 3DLUTs)

    And the rest at the default settings of existing LUT testcharts. That generates a simple profile of 433 patches that will work fine with Novideo_sRGB. As well as having enough accuracy to work with other applications too.

    If you want a serious profile for 3DLUTs (like for DWM_LUT instead of Novideo_sRGB), you need to use different settings. You should set “Dark region emphasis”=20%, “Single channel”=41, “Multidimensional”=0, and “Iterative” to at least 256 (or 512, 1024, 2048, etc – the more the better for 3DLUTs). This copies the Auto Testchart settings while letting you set the 256 “Neutral” patches for better grayscale accuracy.

    You can always press “Sort by HSV” to see exactly what patches it’s generating.

    Hope this helps. And hope it’s not too much info.

    #36823

    S Simeonov
    Participant
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    When I edited the extended testchart for lut profiles with your settings, I ended up with 433 patches, thank you.

    • This reply was modified 2 weeks ago by S Simeonov.
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