LG Ultrafine 5K on Mac mini M1 Keeps Dimming

[gadgetfreak98]

Hi. I have hooked a new LG Ultrafine 5K second gen (27MD5KL) to my new Mac mini M1. Generally speaking it works as expected. The only issue I have had is that occasionally waking from sleep, the screen will be dimmed. This is even though auto-dimming is turned off and the brightness slider is all the way up. When this happens, I move the slider a slight bit and the brightness snaps back to where it's supposed to be.

The LG display utility, by the way, doesn't recognize the connected monitor. I suspect it is not updated for Big Sur and/or M1?

Anyone experiencing anything similar? I'm using the TB3 cable that came with the monitor and it's hooked directly to one of the TB3 ports on the Mac.

Thanks!

 

[pmiles]

Odds are pretty good it's a Big Sur issue... I'd report the bug to Apple so that it gets added to the list of issues to fix (which it likely already is on the list).

Fun thing about a new OS and new hardware... either one could be the culprit... Apple has made this difficult for themselves.

 

[gadgetfreak98]

Thanks. I did file a bug report. I'm not a developer, so not sure how closely regular-people bug reports are followed. But worth a shot, I suppose.

 

[gadgetfreak98]

Continuing to have this issue. Anyone else?

 

[saulinpa]

1st gen LG 5K and have seen it come up at the wrong brightness or even not at all (plug and unplug TB3 cable). Sometimes the brightness keyboard keys don't work. Rumor has it that some LG issues are addressed in 11.1.

 

[roy61]

MacBook Air M1 connected to LG 4K Ultrafine (1st Gen). I have the exact same issue as the OP. Even now I'm on 11.1 but still experiencing the issue....

 

[saulinpa]

Issue not solved with 11.1 but other things are better as haven't had the black screen and the brightness keys have been working. No brightness problems at all on my Intel Mac.

I opened a ticket with Apple. Of course they said no one else had the problem but they did bump it to engineering.

 

[Hessel89]

Of course they said no one else had the problem but they did bump it to engineering.

Typical.

 

[Quackers]

Anything in console logs?

 

[saulinpa]

Anything in console logs?

Good call. Yes, there is some info about setting nits, totally different than on an Intel Mac. On wake it shows nits from before sleep as well as min and max. Then shows "Display 2 setting nits to 200" before showing setting to the previous value. Then shows my adjusting +/- with normal values.

So looks like a fight going on and 200 instead of the previous settings actually gets used.

I have a dark room so 38 appears to be my "normal" setting, Maybe the OP has a bright room and their normal is above 200 so see the monitor dim on wake.

 

[Quackers]

Good call. Yes, there is some info about setting nits. On wake it shows nits from before sleep as well as min and max. Then shows "Display 2 setting nits to 200" before showing setting to the previous value. Then shows my adjusting +/- with normal values.

So looks like a fight going on and 200 instead of the previous settings actually gets used.

I have a dark room so 38 is my normal setting, Maybe the OP has a bright room and their normal is above 200 so see the monitor dim.

So maybe it's a "wake" problem caused by a nit setting? Maybe

 

[Quackers]

Is 200 nits 50% of available nits on a Mac Mini? It would be on an Air but not quite half on a MBP.
I'm thinking it wants to set 50% brightness by default.

 

[saulinpa]

The LG is advertised as a 500 nit monitor. The console info shows maxNits=540.000000, minNits=4.000000, nitsScaler=100.000000, exponent=14. When I adjust it does show going all the way down to 4 and up to 540.

200 as a default makes sense as a simple round number. 37% brightness using this internal scale of 540 max.

 

[saulinpa]

I tried a few more times and caught it when it didn't reset the brightness. The "Display 2 setting nits to 200" didn't show up on the console that time.

 

[Macak]

Maybe thist could help:

Odd behavior in terms of screen brightness

Actually, I guess this has nothing to do with the update. My issue was resolved with a setting. Once I unchecked the Slightly Dim the Display While on Battery Power, the issue has gone away.

forums.macrumors.com

 

[saulinpa]

Maybe thist could help:

Odd behavior in terms of screen brightness

Actually, I guess this has nothing to do with the update. My issue was resolved with a setting. Once I unchecked the Slightly Dim the Display While on Battery Power, the issue has gone away.

forums.macrumors.com

Good thought but this is for a Mac Mini so no battery option in System Preferences.

 

[gadgetfreak98]

By the way, I have replaced my Mac Mini M1 with another (different spec'ed version). The same issue is continuing. And like another person said, 11.1 didn't fix it on the prior or current.

I like to keep my monitor at full brightness. At night, if I choose, I will manually lower it, but during the day time, it is in a bright room and I want to take full advantage of the pricy thing.

How would I check the console nits setting? I'm not familiar.

Also, this has all been reported to Apple engineering, fwiw.

 

[saulinpa]

To look at nits in the console log run the Console app. Click on "Start streaming" then type nits in the search box and hit return. Hit the brightness keys and you will see the data. I set my System Preferences - Energy Saver to Turn display off after 1 min to see what was happening. Note this is for the M1 only as the Intel Mac doesn't appear to use nits.

 

[gadgetfreak98]

Thanks. I did this with console. As some others have pointed out, when it woke from sleep, nits were set to 200, but then a fraction (literally) of a second later, it says it was set back to 540 without my intervention. However, the screen was clearly not at full brightness and I needed to jostle the slider again to get it back to full power. That jostling (moving it slightly from max, then right back to max) showed the brightness declining only to 525. And if I mess with the slider to try to get it as close as possible to 200 (to see if that's actually what I'm seeing from wake from sleep), it seems a bit dimmer than that wake-from-sleep level. But I could be wrong...

 

[saulinpa]

@gadgetfreak98 : You seeing 200 makes it a consistent reproducible bug. Thanks for posting as well as starting this thread. I too think the nits numer is not the exact brightness and seems to vary. Maybe it is combining the nits value with the brightness sensor somehow?

 

[gadgetfreak98]

@gadgetfreak98 : You seeing 200 makes it a consistent reproducible bug. Thanks for posting as well as starting this thread. I too think the nits numer is not the exact brightness and seems to vary. Maybe it is combining the nits value with the brightness sensor somehow?

Well, as it turns out the Apple engineers don’t see it this way. Just got word that it’s a “LG issue” and I should try to speak with them. I suspect that is going to be decidedly more complicated than speaking with Apple Care, but am going to give it a shot and will report back to this forum.

 

[gadgetfreak98]

By the way, I tried connecting my wife's MB Pro with the same TB3 cable. This issue did not recur. She is still on Catalina. I reported this back to my AppleCare senior support rep. No reply yet.

I tried to view the console data as I had on the Mac Mini, but is Console in Catalina different? I couldn't figure out how to monitor the nits data.

 

[njvm]

According to @saulinpa this function is not supported on Intel MBPs, which I assume that is what your wife has if she is still on Catalina?

 

[saulinpa]

Yes, I don't have this issue on Intel Macs. In console there are no "nits" but a "DisplayServicesBrightness" on a scale from 0 to 1. My Intel is also running Big Sur.

 

[gadgetfreak98]

By the way, I’m returning one Mac Mini M1, as I now have one with more appropriate specs for my needs. I did end up wiping the prior one and doing a clean, no user account set up. That too had the issue of the dimming. So I have conclusively ruled out that one specific Mac is at fault. I think the options are:

1. This LG display is faulty
2. The TB3 cable that came with the LG is faulty
3. Big Sur is not fully compatible with the LG 5K
4. M1 Macs are not fully compatible with the LG 5K

I suspect it is #3 and/or #4. The good new for me is that it is NOT an issue of something with my software setup causing the issue...

Oh, and I almost forgot. The weird tearing of the pixels in the middle of the screen happened with the clean set up too.