3D Lut Verification

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This topic contains 60 replies, has 2 voices, and was last updated by  anonymous SourceForge (@anonymous-sourceforge) 4 years, 4 months ago.

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  • #560

    Terrific, I calibrated the monitor manually this time, setting white point and luminance exactly on target. Then profiled again, set everything to max, about an hour of processing.

    Tested in Calman – I get 0.5/1.3, and 0.12/0.39/1.42 in DCG (report attached). And that’s just with an ICC! I then tried Calman Virtual 3D Lut and got 0.4/1 and it was absolutely impossible to see the color difference from the ICC. So that’s awesome. Just wanted to report that.

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    #548

    This “LEd blue green” it’s a GB-LED. In Xrite’s Spectral corrections which you can import with DGS from i1Profiler setup exe, they are called “RG_phosphor”. Eizo CS240 it’s a GB-LED (like new widegamut Dells or NECs) so you MUST apply this correction. Otherwise measurements will be wrong.

    “LCD CCFL Wide Gamut IPS” is an spectral correction for OLD widegamut monitors like PA241W or U2410 so you MUST avoid its use with your monitor.

    In your “before” setting you are validating Eizo CN’s profile, which is a “matrix single curve profile” created with actual post calibration measurement data.
    “Non daylight” white (that little 2dE error) may disapear after you use proper spectral correction for the measurements. You must apply RG_phosphor or some GB-LED equivalent from DCG database. I think that Minolta’s 1nm spectral samples from Xrite are more accurate than Eizo CX271 (same backlight) from DCG database, so I’ll use RG_phosphor or a cleaned version (last 4 spectral samples are from a U2413 GB-LED).

    Your “after” settings I think they are wrong. You calibrate “again” your Eizo in graphics card LUT. Hence the difference: with whatever spectral correction you applied to the process, DCG saw a 2dE error in your hardware calibrated CS240’s white, so in your “after” setting, DCG created a profile with a graphics card LUT calibration to fix it. That 2dE may be not real, because you did not apply RG_spectral correction (GB-LED) to DCG measurements.

    I think that what you wanted to do should is another thing: Apply Rec709 gamma 2.2 as simulation & target profile (without gamma remapping) as Florian said prevously, or if you want to capture actual monitor behaviour in a profile, perform a “profile only” operation which in DCG 3 should be done with a workaround (I think that Florian said that you should set White and gamma “as measured”). In DCG 2.x “profile only” process is easier IMHO. Remember to apply a GB-LED spectral correction before you measure (“profile only” or validation against Rec709 2.2)

    #562

    Florian Höch (@fhoech)
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    Nice 🙂

    It seems the reported dE differences are now down to measurement repeatability limit (which is good). The match to the Calman reported numbers is even better when checking “Absolute results” on the report (avg 0.5, max 1.55), so I think you’re golden.

    #563

    Awesome 🙂

    I tested with a XYZ LUT + swapped matrix first, and it was supported in all Adobe apps, but the colors were green and purple in Chrome (unsupported), so I switched to XYZ LUT + matrix and it’s now fixed.

    I’ve activated Dual Monitor in Speedgrade, so I have my image full screen on the reference monitor. To be sure, do applications in Windows have any other choice but to display their colors through the active ICC profile?

    #564

    Florian Höch (@fhoech)
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    To be sure, do applications in Windows have any other choice but to display their colors through the active ICC profile?

    Depends on the application. The main problem with ICC color management on Windows is that only comparatively few apps (apart from 3rd parties like Adobe which usually have good ICC color management support) actually make use of a ICC display profile, or ICC profiles at all, so the only benefit you get in those apps is from a 1D LUT calibration through the video card gamma tables – this isn’t color management though. Windows apps that are part of Windows itself often have limited display profile support (only profiles with matrix tags are supported by e.g. Windows Photo Viewer), same is true for some 3rd party apps like Chrome. Many open source projects rely on littleCMS though, which is a state-of-the art CMS engine that’s up there with Adobe’s offerings.

    #565

    Okay. But what I created with DCG is a 1D LUT, right?

    Because I do see the colors of my desktop being different since I installed the DCG profile, as well as any app or window I drag in there so… I’m a little confused.

    I always thought an app was either using the ICC profile or not. Or are you saying it’s possible for an app to partially use an ICC and therefore not be 100% faithful to it?

    #566

    Florian Höch (@fhoech)
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    Okay. But what I created with DCG is a 1D LUT, right?

    DCG can create both, 1D LUT and ICC profile. The profile is the “meat”, the 1D LUT is embedded in it (‘vcgt’ tag). Both need to be used together for the profile to yield correct results. The loading of the 1D LUT calibration is handled by the DCG profile loader under Windows (Mac OS X handles it natively), so usually you don’t have to concern yourself with it. Only if you change display profiles in Windows’ color management settings, instead of installing it through DCG, you have to run the profile loader manually to ensure correct 1D LUT calibration state.

    I always thought an app was either using the ICC profile or not. Or are you saying it’s possible for an app to partially use an ICC and therefore not be 100% faithful to it?

    Yes. Those apps have incomplete/broken ICC profile support (they are technically not adhering to the ICC standard), and should ideally not be used for anything color-critical.

    #567

    Thanks I understand better. That’s what I did, I let DCG install and load the profile. I guess I should check with Adobe if the reference window that Speedgrade sends to the second monitor has full ICC support, although I’d be very surprised if it didn’t since a lot of people use it on their GUI monitor.

    Thanks
    Jeremy

    #568

    Florian Höch (@fhoech)
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    I guess I should check with Adobe if the reference window that Speedgrade sends to the second monitor has full ICC support

    With Adobe I’m usually less concerned because their ICC implementation is very good (atleast in their graphics applications like Photoshop), but I have never looked at Speedgrade and it’s certainly good to check if all is working as intended.

    • This reply was modified on 2015-05-20 21:51:10 by fhoech.
    #569

    Thank you

    #570

    From what I’m reading in the forums, some suggest to load the Icm profile as a calibration lut inside Speedgrade. However I find that strange cause it looks right as is with the DCG profile active. I’m trying to find a way to simply test that by eye. If I opened a photo in a picture viewer than fully supports ICC and then switched back and forth between the Speedgrade output, I should be able to verify it. You mentioned something about LittleCMS? Do you know of a picture viewer I could open in Windows, that would 100% inherit the DCG ICC?

    #571

    Florian Höch (@fhoech)
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    For a visual test, you also need suitable test image(s) (with source ICC profile embedded). I’ve attached such an image (if the viewer does use ICC profiles at all, this should look red, not blue).

    Applications that have a working ICC implementation that also makes use of the display profile (this isn’t an exhaustive list, just applications that I know are working correctly as far as I can tell, and for the image file formats I have tested):
    – Adobe Photoshop (any version from CS onwards) for all supported formats
    – XnView (color management needs to be enabled under settings) for formats JPEG, PNG, TIFF, DPX
    – Gimp (color management needs to be enabled under settings) for all supported formats
    – Picasa (color management needs to be enabled under settings) for formats JPEG, PNG, TIFF, GIF

    • This reply was modified on 2015-05-20 23:32:26 by fhoech.
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    #573

    Thanks Florian, I can’t tell you how helpful you’ve been!

    Perfect I will use Photoshop CC then and try your image. I would also like to try a movie still with a rich color palette so I can check.

    So in Photoshop, I should re-save your image with my DCG ICC embedded, correct? Then re-open and select “use the embedded profile (instead of the working space).

    #574

    Florian Höch (@fhoech)
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    I would also like to try a movie still with a rich color palette so I can check.

    What you could do is check against Photoshop, i.e. export movie frame (no color conversion), open in Photoshop, assign Rec.709 gamma 2.2 profile (warning, Photoshop has a “feature” where it uses the sRGB TRC behind your back for anything with a roughly 2.2 gamma TRC and D65 white, so use a D50 Rec. 709 gamma 2.2 profile and assign that).

    So in Photoshop, I should re-save your image with my DCG ICC embedded, correct?

    No, just open the image. When asked if should convert to working space (depends on how you have PS configured) select “No, open anyway, keep embedded profile” (paraphrasing from memory).

    edit attached Rec709 gamma 2.2 D50 profile

    • This reply was modified on 2015-05-20 23:52:55 by fhoech.
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    #576

    Ok. So basically I shouldn’t use the monitor profile. But will it work with D50? I still have the Rec.709 synthetic profile from DCG, could I use that?

    Re: opening the image, you mean “Use the embedded profile (instead of the working space)”. Cause my only other options are “Convert document’s colors to the working space” and “Discard the embedded profile (don’t color manage).”

    So once I have that picture with a Rec.709 profile assigned I can use it both in Photoshop and Speedgrade for a visual test?

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