Screen brightness changing when waking from sleep

That is a known problem with the M1 and the UltraFine. I found that on wake the M1 will send a command to set brightness to 200 nits. You will find this in the console log. I have opened a couple tickets with Apple. First they said it was an issue with the monitor. Then they said they would send it to engineering. Then closed the ticket as unsupported.

I have an LG 5k display. When used with my MBA M1 when waking from sleep it is at a lower brightness than it was before sleeping. When I use the same display with my Mac Mini M1 the brightness never changes so not sure what is happening here.

Note also that this behaviour only seems to occur if the LG Ultrafine is designated the "Main display" (as configured in System Preferences). So if you have two monitors, and one isn't an LG Ultrafine, this may be a work around.

Well for some reason now my Mac Mini M1 has this issue. Every time it wakes from sleep it has a lower brightness than before sleep so does not remember the setting. I have seen that checking the box to auto adjust in the display pane helps somewhat but not really a solution.

I have the same problem. Mac Studio with LG Ultrafine 5k monitor. MacOS 12.3.1 Monterey.

It appears the saved brightness setting isn't lost on wake - just not used, because if I type F1 then F2 (decrease then increase brightness) (or F2 then F1) the old level appears to be restored.

This isn't acceptable behaviour.

I have raised a support ticket with Apple and escalated for engineering response.

Hello, I also have the same problem, I have a MacMini M1 and an LG Ultrafine 4K monitor, I use the brightness to 30% regularly, when the mac wakes up after sleeping due to inactivity it raises the brightness to almost 50%, when I press the F1 or F2 it sharply adjusts to the previously established value, I expect an update with the correction of that error.

carlosoonline wrote:

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I expect an update with the correction of that error.

You won't get that just from posting here.

Readers are almost all other Users like you. Apple does not troll the forums looking for complaints.

Call Apple support, work through the simple steps with the first responder, then ask that your problem be escalated to a specialist. The specialist should create a formal Bug Report, or add you voice to an existing Bug report, increasing its urgency.

Get Support

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mwrourke wrote:

Note also that this behaviour only seems to occur if the LG Ultrafine is designated the "Main display" (as configured in System Preferences). So if you have two monitors, and one isn't an LG Ultrafine, this may be a work around.

That's interesting!

If true, that might be a bug left over from MacBooks, to brighten the built-in display on wake-up.

I can confirm that the brightness is much less likely to be messed up if the display isn't the "Main Display", but it still can occur. It may relate to the depth of sleep involved. I'm finding the display is ok after a short sleep, but not after an overnight one.

I have two LG Ultrafine 5Ks connected to my Studio and yes, the "main" display is the one that acts up most of the time. Strange is that the secondary display sometimes changes after sleep also.