Basic concepts help (Windows 10)

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  • #13764

    Nicola Farina
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    Hi guys,

    I’m quite new to the world of colors so I need some help clarifying me some concepts.

    I’m calibrating two of mine PCs with different setup:
    PC1: Win 10 – 1 display (DELL U2715H)
    PC2: Win 10 – 2 display (DELL U2415 same revision)

    Calibration system: X-Rite 1 Pro with DisplayCAL (Argyll driver)

    Brightness
    My first action was to set brightness to 120 cd/m2 and then calibrate displays (RGB values) trying to stay as close as possible to 120 cd/m2. Is it right?

    Contrast
    Let it set as display default value. Is it right? I’ve read that LCD are not really contrast adjustable.

    Profile or not?
    I installed the generated profiles for my systems displays, but I want to be sure to understand concepts in the right way. Calibration without profile can be considerate a first step to achieve a gamut compliance? Is the profile a final step to correct the delta between calibrated display and real target colors?
    I have notice that if don’t load profiles, some applications show weird colors. If I use a standard display color mode (not custom colors with RGB controls, so a factory calibrated profile), Windows colors look more “conventional” to the way I used to.

    Light grey tent to be a bit bluish
    The quite more understandable point  to me. With calibrated and profiled displays, I notice that some type of greys in Windows look a bit bluish (f.e. the URL bar of the new Chrome material design). This happen with some old Windows applications also: the standard window grey background is much more evident then uncalibrated mode and sometimes seem a bit “bluish” too. This happens more with my PC1 then PC2.

    Is Windows 10 color managed or still depend on applications?
    This continue to be obscure to me. A part from some specific light grey (previous question), I don’t see strange colors in standard applications (Office, browsers, etc.). I know that Photoshop is color managed, but I really don’t understand the difference.

    (PC2) Identical displays not same 100% colors
    I calibrated and profiled the two DELL U2415 (same hardware revision) of PC2 and colors are quite the same (red, green, etc.), but, some type of light grey are a bit more “red” on my right display to my eyes. RGB calibration seems to be right, and both reach 120 cd/m2. Is this possible? If I check the profiles details, I see that the more red display has a bit larger gamut (~1%) than the other. Is this solvable?

    Why DisplayCal Profile Launcher continue to reapplying profiles?
    On both systems, I see that the profile launcher reapplies profiles hundreds of times in a day (I see it from the tray icon popup). Why?

    Thank you very much for your help and for this amazing work on DisplayCAL.

    #13770

    Vincent
    Participant
    • Online

    I installed the generated profiles for my systems displays, but I want to be sure to understand concepts in the right way. Calibration without profile can be considerate a first step to achieve a gamut compliance? Is the profile a final step to correct the delta between calibrated display and real target colors?

    Your displays lack of hardware to achieve this, but you can get a desired white point, desired brightness and desired gamma. That’s what you can get with GPU 1D LUT calibration. Once calibration is loaded in to GPU, DisplayCAL makes a profile recording how that calibrated monitor behaves… a “monitor colorspace” description.
    With that description color managed apps do colorspace transformations. “Profile verification” tests is that profile (that numeric description) and your display behavior match.
    Unless your displays have some “limited gamut” factory calibration (sRGB mode or something like that) it’s very likely that after calibration there will be a small diference between sRGB 255 red and green an your display’s 255 red and green.

    If you want strict sRGB matching for ALL apps in all enviroments you need a monitor with HW calibration powered by lut-matrix-lut hardware at least, better if it has LUT3D (actual LUT3D, some of them advertise it but they don’t have it, they just have lut-matrix-lut).

    I have notice that if don’t load profiles, some applications show weird colors. If I use a standard display color mode (not custom colors with RGB controls, so a factory calibrated profile), Windows colors look more “conventional” to the way I used to.

    Color managed apps’ limited precison and some graphics card hardware/drivers make rounding errors while working in 8bit per channel. This may fall into your generic description of “weird colors”, very easy to happen in greys.
    Better GPU (high bit depth and dithering), idealized profiles (single curve + matrix) and better apps (temporal dithering like Lightroom or CaptureOne) lower these errors, even make them invisible.

    Light grey tent to be a bit bluish
    The quite more understandable point  to me. [..]

    Chrome is some of those apps with bad color management.
    If you see these issues in Windows desktop then it could be related to graphics card hardware/driver, typical from intel iGPU or nvidias… or bad calibration loader app. Make user that you only use DisplayCAL calibration loader app.
    Banding in smooth gradients in non color managed enviroments while using DisplayCal tray app is a smoking gun for GPU related issue (HW or driver issue). You cannot fix it unless you get a better GPU (I mean less prone to these errors: AMDs are very good at this) or a display with HW calibration.

    Is Windows 10 color managed or still depend on applications?
    This continue to be obscure to me.[…]

    I think that “Not color managed by default” would be the more accurate way to say it.
    Not color managed apps output RGB numbers unmodified to display (GPU 1D LUT corrected).
    Windows just “publishes” to apps which display profile is asociated to each display. Apps should use these profiles with a color management engine, their own engine or the one provided by MS (AFAIK).

    Color managed apps transform each RGB color (defined in a known colorpsace) to “equivalent” RGB number in your displays colorspace. For exampe sRGB 255 red could be equivalent to RGB (253,2,2) in your display. Same color, different numbers.

    This could be good or bad… it’s up to what you want to do.
    It is good if your own a display able to “clone” other device’s behavior (LUT3D HW calibration), it is good if you do not want to suffer some rounding errors in UI gradients.
    It is bad if display colorspace is very different from sRGB and you want to use Office (for example).
    YMMV … I like more “non color managed by default” approach than OSX rounding errors in its color managed UI. IMHO a UI is better if it is smooth (not corrupted by banding) than color accurate but you can like the other approach.

    (PC2) Identical displays not same 100% colors
    I calibrated and profiled the two DELL U2415 […]

    This could be raletd to:

    -calibration rounding errors (explained above)
    -slight different backlight spectral power distribution between your two U2415
    -i1 Pro inaccuracies.

    Try to generate a CCSS with 3.3nm resolution with your i1Pro for each display.  Make actual measurements with an i1DisplayPro (or i1d3 versions) and CCSS you made for each display.

    Another option is to use 3.3nm mode while fixing RGB gain to get the same white.

    Also you can try to match the 2nd display visually in white, then choose “whitepoint” as measured for that display.

    Why DisplayCal Profile Launcher continue to reapplying profiles?

    To ensure that no other calibration cleans GPU 1DLUT with calibration: games, full screen video players…

    … or to apply a different calibration per user’s request. For example another profile set as “default” in Windows control panel / color management for that display.

    • This reply was modified 4 years, 2 months ago by Vincent.
    • This reply was modified 4 years, 2 months ago by Vincent.
    • This reply was modified 4 years, 2 months ago by Vincent.
    • This reply was modified 4 years, 2 months ago by Vincent.

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    #13783

    Nicola Farina
    Participant
    • Offline

    Light grey tent to be a bit bluish
    The quite more understandable point  to me. [..]

    Chrome is some of those apps with bad color management.
    If you see these issues in Windows desktop then it could be related to graphics card hardware/driver, typical from intel iGPU or nvidias… or bad calibration loader app. Make user that you only use DisplayCAL calibration loader app.
    Banding in smooth gradients in non color managed enviroments while using DisplayCal tray app is a smoking gun for GPU related issue (HW or driver issue). You cannot fix it unless you get a better GPU (I mean less prone to these errors: AMDs are very good at this) or a display with HW calibration.

    I’m trying to calibrate another time the PC1 display and I noticed that I can achieve a good calibration (green delta message and R,G,B sliders in the middle) with different RGB values on the OSD display controls. In detail:
    R: 100 G: 99 B: 100 and brightness 22
    but also
    R: 98 G: 95 B: 99 and brightness 23 (a bit less perfect in the middle for all three sliders, but always green goal)
    But, with this second setup, the bluish effect of some specific light greys are gone!

    Is it normal? I was thinking that the right RGB combination was only one, not more. I suppose can be the backlit panel acting in not a reliable way due to different RGB values that are set in the OSD controls (or GPU rounding issues for that colors?). If I thinking right, how can one determine the best RGB settings if different combination can achieve the same good result? Actually, I’m judging this second calibration better because I don’t see the bluish effect anymore, but is a “by eyes” evaluation.

    Many thanks for your patience.

    #13789

    Vincent
    Participant
    • Online

    Light grey tent to be a bit bluish
    The quite more understandable point  to me. [..]

    Chrome is some of those apps with bad color management.
    If you see these issues in Windows desktop then it could be related to graphics card hardware/driver, typical from intel iGPU or nvidias… or bad calibration loader app. Make user that you only use DisplayCAL calibration loader app.
    Banding in smooth gradients in non color managed enviroments while using DisplayCal tray app is a smoking gun for GPU related issue (HW or driver issue). You cannot fix it unless you get a better GPU (I mean less prone to these errors: AMDs are very good at this) or a display with HW calibration.

    I’m trying to calibrate another time the PC1 display and I noticed that I can achieve a good calibration (green delta message and R,G,B sliders in the middle) with different RGB values on the OSD display controls. In detail:
    R: 100 G: 99 B: 100 and brightness 22
    but also
    R: 98 G: 95 B: 99 and brightness 23 (a bit less perfect in the middle for all three sliders, but always green goal)

    There are several combinations with the same white balance as all three RGB gains go to zero… and with each down step, contrast is expected to go down too.

    But, with this second setup, the bluish effect of some specific light greys are gone!

    Before or after calibration?
    If this happens after calibration a slow speed configuration may solve it (unless you have some issues with GPU loading calibration in the right way)

    Is it normal? I was thinking that the right RGB combination was only one, not more.

    Before calibration blue tint in greys?
    It could happen… RGB gain & contrast controls are a black box. Only manufacturer knows what parameters are controled with them.

    I suppose can be the backlit panel acting in not a reliable way due to different RGB values that are set in the OSD controls (or GPU rounding issues for that colors?). If I thinking right, how can one determine the best RGB settings if different combination can achieve the same good result?

    A grey black to white gradient being show on a small MS  Paint window at the same time you see DIsplayCAL 3 bar for white point during calibration.
    Squares with whites from 240 to 255 may help too.
    The less color issues you see in that gradient / white squares, the better.

    GPU or calibration loader app issues related to rounding errors will be show after calibration… unless you are trying to send HDMI TV levels to those monitors, change color controls in GPU control panel or some related misconfiguration.

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