Catalina's HDR bug with external display

XNorth

macrumors regular
Original poster
Feb 23, 2018
245
139
United States
The LG 34WK95U is a beautiful HDR10 capable display. Using the LG in DisplayPort 1.2, it is native 5120 x 2160 21:9, and it's gorgeous scaled to 3440 x1440. I have been waiting for Apple to fix HDR so I can finally use HDR on the LG.

Catalina 10.15.14 supposedly improves HDR on external displays and TVs. I updated to 10.15.14 and tested HDR mode. Spoiler: HDR is still shitey for external displays.

Catalina 10.15.14 HDR issues:
  • Switching the LG from DP 1.2 to 1.4 to enable HDR while it’s connected to the MBP, the display goes black. Unplugging and resetting the power brings the display back on. (Only DP 1.4 supports HDR).
  • Because of issue #1, I can only switch to DP 1.4 before connecting the TB 3 cable to the MBP. Once the TB cable is connected in DP 1.4, HDR kicks in and the HDR mode notification appears briefly in the upper right corner of the display.
  • In HDR mode, the display is noticeably less contrasty and washed out.
  • In the Displays Preferences, the available resolutions of the LG max out at 3840 x 2160, which is 16:9 aspect ratio.
  • Display scaling doesn’t work properly. For instance, to get 21:9 aspect ratio back, I scale to 3440 x 1440. But that now becomes the effective resolution of the display, not just for the UI.
The HDR bug basically reduces my color-calibrated 5K 21:9 monitor to a 3K 16:9 monitor with bad HDR color. I will continue to use DP 1.2 and avoid HDR on my external display for now. Catalina is not ready for HDR.

Screen Shot 2020-03-25 at 9.30.19 PM.png
 
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weichsel

macrumors newbie
May 23, 2013
15
5
I am using a LG 27UL850-W connected to a 16'' MBP. With HDR enabled in 10.15.4, I also get washed out colors (with a blue tint).
Is someone using the OnScreen Control software that LG provides in the download section of their website (https://www.lg.com/us/support/software-firmware-drivers) I noticed my display's OSD menu deactivates several functions when HDR is activated in macOS - Maybe that control software is necessary to get proper colors in combination with HDR?
 
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weichsel

macrumors newbie
May 23, 2013
15
5
The link doesn't work.
Fixed.

HDR disables settings that it automatically controls or not needed.
Maybe those automatic controls don't properly work yet for 3rd party displays (The XDR seems to have gotten some HDR specific UI in the Display Preferences).
 

Superhai

macrumors 6502
Apr 21, 2010
440
348
I have a 2018 Mac mini connected via HDMI to an LG TV. If I use my Intel UHD graphics, HDR works properly but only in 1080p. If I switch to 4k, HDR option disappers altogether (this is a limitation Apple have specified on their website).

I have an egpu with AMD Radeon VII, and here I get HDR in 4k, but colors are washed out, and the TV is not detecting HDR mode. But watching HDR10 content is displayed correctly.
 

XNorth

macrumors regular
Original poster
Feb 23, 2018
245
139
United States
According to that Apple support page, all Macs from 2018 or later, except the mini, support HDR at 1080p and above with DisplayPort.

Is someone using the OnScreen Control software that LG provides in the download section of their website
LG True Color Pro will crash or not complete calibration. Doesn't seem supported in 10.15.4.

I'm able to get better HDR color and contrast using the Spyder5 Elite calibration device. But the color red is dialed way up, no way to bring it down to normal levels. Anything in red is blown out and oversaturated. As a comparison, Apple TV HDR looks much better on my LG C9 TV, the way it should look,

SwitchResX restores 5120 x 2160 resolution to my LG display in DP 1.4, though it does not fix the scaling problem. System Report still shows the max resolution as the scaled resolution.
 

Superhai

macrumors 6502
Apr 21, 2010
440
348
According to that Apple support page, all Macs from 2018 or later, except the mini, support HDR at 1080p and above with DisplayPort.
Yep, and the HDR support is limited by the Intel HD graphics. It seem there is something funky happening with the AMD drivers when using HDR on certain displays.
 

clarksonknight

macrumors regular
Aug 15, 2008
105
1
Washington, DC
I don't have an HDR display, but do have an LG UltraWide USB-C 34" monitor that is having similar kinds of issues. I posted this in the Catalina bugs thread as well, but it's been driving me nuts all day. My work MBP (2018 model) updated to 10.15.4 last night, and now the LG display is washed out and all options except for brightness and a handful of presets are disabled. A couple of the non-default profiles improve it, but it's still terrible. I tried installing the LG software, but that didn't have any options that improved anything, nor did clearing the NVRAM.

My personal MBP (16" model) is still on 10.15.3 and the monitor picture is fine when connected to that machine. All picture settings are available when my personal MBP is connected.

EDIT - This thread: https://discussions.apple.com/thread/251213356 helped me resolve the issue. Took a bunch of restarting my MBP and resetting the monitor, but eventually the new HDR option showed up so that I could disable it and get my monitor functioning normally.
 
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XNorth

macrumors regular
Original poster
Feb 23, 2018
245
139
United States
Don't use DisplayPort 1.4 if your external monitor has the option to switch between DisplayPort 1.2 and 1.4. Catalina 10.15.4 automatically enables HDR mode in the Displays Preferences if your monitor is in DP 1.4, and most of the picture adjustments in the monitor's OSD will be disabled.*

HDR mode for external monitors has too many issues. It's not worth it until Apple fixes it. My HDR monitor's color, brightness, and resolution are much better without Apple's poor HDR implementation.

*Edit: If your monitor can't switch to DP 1.2, you can simply uncheck HDR in the Displays Preferences. But be aware that Catalina could automatically check the HDR preference if your monitor is in DP 1.4.
 
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