LG G5 3D LUT Upload doesn't match Active LUT?

Hello,

Whenever I upload a LUT to the 3D slot in my G5, it seems to not match what I get when using the same LUT in Active LUT, in a visually obvious way. Measurement wise, I'll see changes, but the greyscale seems only slightly affected by it. If I upload the same LUT to the 1D slot and put the 3D LUT back to Unity Bypass, it looks and measures exactly the same on the greyscale as if I were using Active LUT.

It was my understanding from reading the guides on this site that I should be able to only upload a 3D LUT and accomplish full calibration with greyscale included and I can leave 1D on Unity Bypass. Would anyone have any pointers for what I might be doing wrong? It almost seems like the TV is not reading the 3D LUT correctly, but I've seen other posts of people calibrating their G5's with 3D LUTs seemingly without issue, though I've run out of ideas on what I could be doing wrong.

There are a number of possible/probable reasons.
Most 3D LUTs have a coarser granularity than the 1D, which is why using Lage LUT sizes in ColourSpace works well when the 1D is treated separately to the 3D.
https://lightillusion.com/lut_size.html
Alternatively you may have a range mismatch - Legal vs Data ranges.
https://lightillusion.com/data_legal_levels.html
https://lightillusion.com/issues_lut_processing.html
https://lightillusion.com/issues_signal_processing.html
https://lightillusion.com/issues_signal_range.html

Steve

Hey Steve. Thank you for the response. I will review all of those, I think I hadn't seen one or two of them. I'm stuck on the smaller LUT size with HTL, but I at least don't think it's a legal vs data range thing. At one point I tried using the Video Scale feature in the LUT generator; it was pretty much the same story. Uploading that to the 1D LUT slot produced an obvious change reflecting the change in scale, with the display having an elevated black level afterwards, and very little effect to the greyscale when uploading to the 3D LUT.

The LGTV Integration Guide says:
"Note: Due to some LG firmware issues, it may be necessary to switch to a different picture mode and back again, or even power down the TV, and unplug for a while, to activate the uploaded LUT.
Also verify the correct settings for the LUT upload, such as Colour Space, etc."

In fact, I had to unplug the TV to get it to work properly.

So, I have looked over the issues guides linked and also turned off and unplugged my LG G5 for over 10 minutes. When it came back up, it still seemed like the 3D LUT had a very miniscule effect on the picture, if at all.

Any other ideas? It is very strange that I can upload this LUT to the 1D slot and have an immediate, obvious change in the image from the very cool native white point being corrected to that of Rec2020, but nothing like that happens at all when I upload it to the 3D LUT

Have you checked that the TV is not still set to 'Wide Colour', or whatever the setting is, after the LUT is uploaded?
That is explained in the User Guide, as already stated by Wolf91074.

"Also verify the correct settings for the LUT upload, such as Colour Space, etc."

Steve

The internal LUTs in LG televisions operate within the 64-1023 (EXTENDED) range.

Therefore, when profiling 1D or 3D LUTs, it is necessary to use a EXTENDED signal and corresponding patchlists while the television's contrast is set to 85.

Regardless of whether the calibration singal that you want to feed the TV after the calibration (VIDEO or FULL), profiling must be conducted using the EXTENDED range with an RGB signal rather than YCbCr.

LG televisions do not support FULL range profiling. To achieve full range, profile using the EXTENDED setting with 4:4:4 processing enabled in the LG menu, and subsequently verify using full range.

No scaling filter is required when applying the generated LUTs.

An alternative calibration method requires a videoscale filter and a contrast setting of 100; however, these steps are not necessary to complete the current calibration process.

I did not, no, I apologize. I misunderstood and thought that was referring to the colour space setting in ColourSpace (Rec2020 vs Rec709), in the same box as the LUT slot selection and the picture mode. I will fiddle with that later today after work.

This is all good to know; is it also the case for HDR or just SDR? I probably should've mentioned before that all this is happening with HDR. I apologize for that as well, and thank you both for your replies.

I've made that more apparent in the LG guide now.

There is also info on the range the LG uses in the User Guide page.



Steve

Hi Steve. From what I've tested, and from what I've gathered from speaking with some calibrators, there is a bit of a caveat with setting the LG OLEDs to Contrast Ratio 100.

It would appear that if you set black level any higher than 50 (often required on these OLEDs in SDR) AND you have contrast ratio 100, it will actually introduce some clipping near-white, clipping off CV 234 (8 bit scale.)

Additionally, at least on the C4, yellow color luminance suffers with CR100 as well (even at BL50.) Setting CR to 92 fixes this.
Now this is where I am going to quote someone since my own knowledge is fuzzy, but according to him:

"Problem with CR100 is that yellow undertracks to a noticeable extent, more-so on my display: (-8%/92%). On yours, it only seems to be -4%, possibly due to your AWP. Usually the 'correct' choice is to scale down just the neutral axis to maintain additivity, but it seems like your 3DLUT generation did not do that. Neither does DisplayCAL. Anyway, bringing the CR down to 92 while having the same 3DLUT applied was enough to give yellow enough headroom to fall in line (of course at the cost of some white brightness. Ideally this shouldn't have been needed, since the 3DLUT generator should just pull the neutral axis down)"

Figured I'd mention these nuances in case they are interesting to you.

If you read our user guide we do not mention calibrating to full range.
The TV just can't do it properly.
But that has nothing to do with ColourSpace.
And the rest is not something you set within the LUT generation.
No idea who is suggesting that, but it seems they don't understand calibration basics?

Oh, and a colourimeter can't actually have an issue with a secondary colour, as they are primary filter based.
So that in itself makes no sense.

Steve

I will gather more info on the yellow luminance issue before posting more about it, in case I misrepresented something, which is definitely possible.

As for the BL >50 and CR100 thing, from what I've tested, it seems that this combination clips off CV 234. The issue goes away with BL50 and CR100. This occurs even after calibrating the TV properly (sending rgb full signal from pgen, and having the TV set to limited.) I had edited my comment above but you were too fast , since I think I was being confusing by mentioning using rgb full with a PC. This happens regardless of whether I use ycbcr or rgb full in windows (in the nvidia driver you can set the signal output as rgb or ycbcr.) I only mentioned Windows since it's where I typically view a lot of clipping patterns. But the issue is there even outside the PC, just using pgen sending rgb full, and TV limited, manually showing patches.

For clarification, whenever I do the actual calibration, it is always pgen sending rgb full, and TV set to limited.

Doh! I read CR100 as the probe!
But - the same actually hold true for a display - in theory - as that is a RGB device too.
So in 'theory' no primary colour can ever be anything except a direct equation of the primary colours.
Except...
WOLEDs obviously has an addition white pixel, and that is not a pure 'white', so as that comes into play more there will be a decoupling of the secondary colours from the primary.
And yes, altering the target white point will alter what that deviation is.
But, that's not really related to clipping, unless one or two of the RGB channels is clipping before the other channel(s).
However, all calibration is subtractive, so it can't 'add' colour at all.

Not sure if that is related to what you are trying to describe though, as I think I must be missing something from your descriptions.

Steve

I just got home and checked the color settings on the TV itself, it is indeed set to Wide, but that option is greyed out and unable to be changed. I've already left it unplugged for 10+ minutes before to try to get the 3D LUT activated, and I've tried switching around picture modes as well. I'm feeling like I've done something fundamentally wrong. The only thing that seems to work right is uploading to the 1D LUT slot.

For the signal ranges, I did the calibration in legal range using a PGenerator set to RGB Full, ColourSpace patch set range to Legal, and I say the black level on the TV to Limited just to ensure Auto didn't pick the wrong one. I can try doing extended instead with the lower contrast setting, but I wouldn't think that would make so much of a difference to where the 3D LUT seemingly doesn't work at all, only the 1D LUT, would it?

BIG EDIT: Nevermind! Today I set out to fiddle with every single setting on the TV to see if any of it would make the LUT take effect. I even downloaded the LUT to see if it matched what I thought I uploaded and it indeed did. Nothing would get it to work. I made a couple of LUTs where I flipped the hue 180 in GIMP so I could easily tell if anything would work at all or not, uploaded it, still nothing. I even spent about an hour digging around via SSH (my TV is rooted) to see if there was a log giving an error of some kind, and saw the LUTs I uploaded on the filesystem with dates that seemed to reflect when I uploaded them, but still nothing. Finally when I issued reboot in the terminal, which I SWEAR I've done before because you can hear the power supply click off and back on when you do this and I thought it'd guarantee a genuine full reset, it came back up and my colors were all crazy / the 180 Hue LUT had taken effect.

Reuploaded the calibration LUT, SSH'd in and issued a reboot once more, and this time it came up looking very-obviously-calibrated! I have no clue why it worked this time and didn't before. Thank y'all so much for all the help so far, I think now I know to just maybe retry an upload and then reboot right after it until it eventually works, which is crazy but at least it works. Now I need to go rent a spectro from someone so I can probe match and then really go to town on it.

A rooted TV has many potential issues...
Probably should have said that from the start.
Glad you sorted it.

Steve