How to target a certain gamut and gamma?

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  • #10747

    Isaac Barahona
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    So I just bought a new monitor, MSI Optix G27C2.

    I already have created a profile for desktop/browser/gaming use with the sRGB tone curve, I’ll attach it below.

    Since I don’t game that much but I do watch a lot of rec.709/bt.1886(BD rips) content I’m more interested in if it’s possible to create a “rec.709/bt.1886” icc profile for my monitor and how?

    I’m using the Spyder5 and DisplayCAL 3.5 on Windows 10 v.1709 and my gpu is an AMD RX 480gb.

    Thanks.

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    #10755

    Vincent
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    That seems to be one of those new QD LED monitors with extended gamut beyond sRGB.
    GPU LUT calibration is limited to fixing white point, grey neutral to that white and your desired gamma. After this calibration a profile is created with actual calibrated monitor response. Color managed programs know how to “map” sRGB colors (sRGB “numbers”) to the colors of the colorspace (numbers, again) described by that icm profile you created.
    Other programs can even use a computed table (LUT3D) that does such work.

    So if you want to see Rec709 content in a monitor with a native gamut bigger than sRGB:

    -use a color managed video player, like MPC with DirectX9 render and use it’s embebed color management
    -use a video player that can use LUT3D,  like MPC with madVR. DisplayCAL could create such LUT3D for you.

    If you want “desktop rec709” on Windows:
    -check if your monitor has some “sRGB mode”, then calibrate that osd mode like you did. DisplayCAL won’t fix gamut with a GPU LUT calibration. Gamut will stay the same as it is in such mode: DisplayCAL can fix, white point, grey colors to have the same tint as white and gamma, just that.
    -you can use one of the special features of AMD GPUs: disable “color temperature” on Catalyst/Crimson configuration and it will map desktop color numbers (supposed to be sRGB-like) to “numbers” in monitors EDID native colorspace. If EDID info is not accurate such transformation won’t be accurate. I think that you can enable such mapping and keep GPU LUT calibration active (try to make a calibration with such mapping active).

    • This reply was modified 6 years, 1 month ago by Vincent.
    #10757

    Isaac Barahona
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    That seems to be one of those new QD LED monitors with extended gamut beyond sRGB.

    I don’t think it’s a QD LED monitor because MSI doesn’t advertirse it as such(it’s a good selling point), but it does go beyond sRGB as you can see in the image below:

    I use mpv for playback, it can also use 3DLUTS.

    I don’t quite understand what are you trying to explain me(I’m new to calibration), I just want to know if I can calibrate my monitor to the bt.1886 gamma with the bt.709 gamut. I don’t understand why I would need a 3DLUT if my monitor exceeds the bt.709 gamut, colors wouldn’t clip because my monitor can represent all the bt.709 gamut, right?

    #10759

    Vincent
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    I just want to know if I can calibrate my monitor to the bt.1886 gamma with the bt.709 gamut.

    Unless MSI provides a software to make such calibration inside your monitor (it does not seem to be your situation) or your monitor has some OSD mode called “sRGB” which gamut is very close to sRGB/Rec709 then the answer is NO.

    BUT you can watch sRGB/Rec709 content rendered accurately on that display in the way I said to you: video players with LUT3Ds or profile based color management:

    I don’t understand why I would need a 3DLUT if my monitor exceeds the bt.709 gamut, colors wouldn’t clip because my monitor can represent all the bt.709 gamut, right?

    In order to keep it simple, let’s think in 0-255 range. It’s just an explanation.
    If you have an sRGB image with “0,255,0” green, and you send those numbers to your monitor (with a gamut bigger than sRGB in green and red) it won’t render like “sRGB’s 0,255,0” but a more saturated one… and you do not want it since you want content to look like it was intened to display.
    Color management comes to your rescue: it takes such sRGB 0,255,0 as input but it outputs other different numbers that for YOUR display will give you the same color as sRGB 0,255,0.
    This could be done with profile (icm) based color management like Photoshop or GIMP, or with a LUT3D like some video players.
    Think in the same way for content encoded in legal video range.

    That’s why you need LUT3D or a video player that supports profile based color management like the one you use.

    I do not use MPV, but I’m sure that in its documentation you will find how to provide your monitor’s ICM profile so MPV will do what I’ve explained above: map content colorspace “numbers” to other different numbers in monitor’s colorspace that represent “the same color”.
    The same goes to LUT3D if that video player supports them.

    #10825

    Isaac Barahona
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    Thank you for your response Vincent, mpv does support 3DLUTS so I’ll make use of them but I have one more question.

    Which type of “Rendering Intent” would work best for mapping BT.709/BT.1886 content to a wider gamut display(wider than bt.709, like my monitor), mpv only supports perceptual, relative colorimetric, saturation and absolute colorimetric.  Which of those four types would work best for my display?

    #10832

    Florian Höch
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    Which type of “Rendering Intent” would work best for mapping BT.709/BT.1886 content to a wider gamut display(wider than bt.709, like my monitor), mpv only supports perceptual, relative colorimetric, saturation and absolute colorimetric

    Perceptual (unless you want BT.1886) or relative colorimetric (absolute colorimetric if your display whitepoint isn’t D65 and you want the latter). Note that rel.col. + BPC, perceptual and saturation will give the same result (all the rendering intent selection in consuming software does is tell the CMM which table to use in cLUT-based profiles. DisplayCAL by default only creates colorimetric and perceptual tables, with perceptual being equal to rel.col. + BPC).

    #10833

    Isaac Barahona
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    Why Perceptual? In DisplayCAL’s documentation says  “This intent is useful if the destination gamut is smaller than the source gamut.” This case is totally the oposite, isn’t it? My monitor gamut(destination) is bigger than the source gamut (bt.709).

    I’ve also already created a profile with the BT.1886 tone curve for my monitor so I should set the tone as “Unmodified” in the 3DLUT tab, right?

    Also in the mvp’s logs files I get this warning “ICC profile detected contrast very high (>100000), falling back to contrast 1000 for sanity. Set the icc-contrast option to silence this warning.” This warning means the contrast ratio isn’t stored in the icc profile, is there a way to store the contrast ration in the icc profile with DisplayCAL?

    #10834

    Florian Höch
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    In DisplayCAL’s documentation says “This intent is useful if the destination gamut is smaller than the source gamut.”

    This applies when using a large source colorspace, and either creating a 3D LUT or using CIECAM02 gamut mapping to create a perceptual table for a display profile.

    Note that the rendering intent setting in MPV does not apply to 3D LUTs.

    I’ve also already created a profile with the BT.1886 tone curve for my monitor so I should set the tone as “Unmodified” in the 3DLUT tab, right?

    No, you always choose the curve you want, regardless of what the monitor’s response is.

    #10836

    Isaac Barahona
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    Thank you for your response Florian, I kind of get it now.

    #10837

    Isaac Barahona
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    So I just gave the mpv documentation a good read and it looks like you can’t load an external 3DLUTs on mpv because it creates it’s own for each type of video.

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