Unable to verify 3DLUT

[Antonio Marcheselli]

Hello all,

I’ve recently acquired an old LG C7 OLED TV and I am trying to profile it. I think I am familiar with the workflow, I was able to profile my VPR before I got the TV.

On this occasion, I managed to get a good result by adding a full field 25% insertion every 5 seconds to try to stop LG’s automatic brightness adjustment and also selecting “maximise lightness difference” under profiling.

If I verify the profile using DisplayCAL, I get a good result (I think). My dE averages 0.77.

But if I play a grayscale via MPC-HC and read it via HCFR (with 3DLUT enabled) I get poor results. 50% as an example has a dE of 2.6

I am a bit lost as I don’t see how that is possible. I’ve done that before with my VPR and it normally works!

This is an HTPC, the TV does not change anything when MPC-HC starts, not even framerate.

Gamma ramps are disabled in MPC-HC and gamma is included in the 3DLUT file as I usually do.

Any inputs is appreciated! Thanks.

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[Antonio Marcheselli]

Apologies for selecting the wrong forum – this should have been help and support.

can anybody help please?

[Vincent]

You are not verifying profile, but uncalibrated display.
You do not show madVR config or HCFR reference.
You did not test LUT3D though displaycal using equivalent device link.
You did not test LUT3D though displaycal using madVR output with LUT3D enabled.

Usually if you want a LUT3D you use full native gamut in your OLED.
Custom OSD modes with CMS and 10-20 point or restricted to some colorspace are meant to be tweaked in HCFR to use TV without further computer correction.

[Antonio Marcheselli]

Thanks Vincent for your input, it’s very much appreciated. I am not sure I fully understand all your points, I am doing my best! 🙂

First, I am not sure why you’re saying I did not test via madVR? When I run the verification section (measurement report), the madVR TPG appears on screen to display the patches. 3DLUT is not disabled.

When I run patches via MPC-HC, this is via madVR, 3DLUT enabled. Yes, I am not running the TPG at that point but that is the whole point of my test: test my work with actual test patterns run via madVR. In that case I use HCFR just as a tool to read the colours. If the readings are not as expected, then there is something wrong with the workflow. It worked in the past, it doesn’t work now so something is not working here! 🙂

Regarding using the TV controls to calibrate the video, I have indeed calibrated the TV via its own controls before running DisplayCAL for a very good reason: I have other sources than the PC and I’d like them to look as good as possible. DisplayCAL will apply its 3DLUT on top of what the TV is doing.

HCFR reference is attached but I don’t think it matters: I forgot to say that the white balance does not look linear . MadVR config is attached as well.

One thing I noticed with this OLED TV is that it seems to be very unstable. Brightness and colours seem to change depending on many factors (APL, temperature, size of the test pattern). I have disabled what I could from the service menu but I am wondering whether this TV can be calibrated at all!

Thanks again for your input.

Tony

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[Vincent]

You are right, I misread 1st screenshot, it was read using madVR.

Try to use as verification testchart extended grayscale test chart to spot gamma or color errors.

[Antonio Marcheselli]

Just to update on this, I think my very basic mistake here was that I was using an OLED correction curve in displayCAL and nothing in HCFR. I have now corrected my instrument using a reference one in both software. I haven’t tested yet but I am confident that that was the issue.

Thanks!

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