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Uploading LUT to HDR Profile results in very dark picture for LG 27EP950 [Updated]

 
Author erazortt
ZRO
#1 | Posted: 23 Apr 2023 15:00 
Uploading a LUT to either of the HDR Picture Modes results in a too dark picture (about half as bright as expected).
That is not only the case for my own LUTs but the same is true when uploading the Unity Bypass or Default Unity LUT. The brightnesses are ~300nits when "Peak Brightness" setting was set a "Very High", ~250nits at "High" and 175nits at "Normal".
Using version 1629.

I think somehow related is the issue that the "Peak Brightness" setting for the HDR Profiles overwrites the setting for SDR, which should however never be different from "Normal". To check this look into the displays OSD, there the Peak Brightness setting for the SDR modes should always show "Normal" independently of the setting when in a HDR mode. And actually by default, this setting is even grayed out in the OSD for the SDR modes after a factory reset, but once a LUT was uploaded using ColourSpace this setting becomes active for SDR, which is not the right behaviour.

Author erazortt
ZRO
#2 | Posted: 18 Jun 2023 20:53 
Version 1685 now somehow fixes the situation for HDR.
However once the HDR profile is uploaded, the previously uploaded SDR profiles are all being increased in brightness. It appears that now the "Very High" brightness setting from HDR is taken over to SDR.

How to reproduce:
1. Switch to sRGB using the "Picure Mode" setting in the "LG Pro Options" panel in ColourSpace
2. Upload a LUT
3. Switch to "HDR BT.2100 PQ" again in the "LG Pro Options" panel
4. Set the Brightness setting to "Very High"
5. Upload the "Unity Bypass" LUT
6. Upload the desired LUT
7. Switch back to sRGB
8. The profile is way too bright, since apparently now here the "Very High" brightness is also applied. This can be valided by the fact that now in sRGB there is ABL kicking in.

Author Steve

INF
Male
#3 | Posted: 21 Jun 2023 11:43 
We have looked at this, trying to replicate the issue, following the instructions as provided.
We cannot get our LG to demonstrate this issue...
We therefore believe this may be a firmware revision issue.

There are only 3 modes that allow bright and super-bright luminance, those are the 2 PQ slots and the calibration slot.

The other factory slots are specifically prevented (by LG) from operating in any mode other than standard brightness.

On our monitor, it works exactly as expected both from CS GUI and from the LG OSD.

We need further details, firmware rev, etc.
Maybe a video showing the monitors OSD settings?

It would be best to hard reset the monitors picture modes before running a test, as well as making sure the latest LG firmware is installed.

Steve
Steve Shaw
Mob Boss at Light Illusion

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 Uploading LUT to HDR Profile results in very dark picture for LG 27EP950 [Updated]

 

 
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