After upgrading to Catalina, MacBook Pro ups its screen brightness to max every time I connect an external monitor (any external monitor). Is there a solution? I am using manual brightness.
MacBook Pro with Touch Bar
I usually do not restart MacOS unless I have an update or something. I connect and disconnect external monitors when needed. Even if I do not physically disconnect a monitor, but turn it off with a button and then turn back on again, the built-in monitor goes into full brightness. This was not the case with OS versions prior to Catalina and is clearly a bug. This is not critical bug and I can live with this. I am a Software Developer and I do this for a living. If Apple pays me to help localizing this bug fix this, I can spend time on this task. But otherwise - no worries.
It really did take far too long to resolve, and it seems as of right now the fix is specifically mentioned for the LG 5K. I know of at least two published reports it also occurs with the new Pro Display XDR on the 2019 Mac Pro.
It might have helped (I hope) that this issue received mention on Lloyd Chambers Mac Performance Guide, John Gruber's Daring Fireball and other places here and there.
Happy News = It's Fixed 😊 after Installing macOS 10.15.4 Update!!!
I did 1 Restart to make sure that this Fix is real! It is 😊 !!!
The Brightness on my MacBook Pro 15’, Late 2017 stayed where I left it off before the Restart 😊 !!!
Thanks Apple 😊 !!!
Below is my Setup:
MacBook Pro 15’, Late 2017, macOS 10.15.4
I use Thunderbolt Display with it, via Thunderbolt 2 to 3 Apple Adapter.
My HDs are plugged in via OWC Thunderbolt 3, 13 Port Dock, which is plugged in via USB-C into MacBook Pro!
You do know that Apple representatives are not here. We're all users like yourself. If you want to tell Apple of your problem use Feedback - macOS - Apple
I had this problem and just chatted with support. They recommended to reset the SMC. See instructions here: https://support.apple.com/en-us/HT201295 This worked for me.
I can confirm it works fine when:
a. Automatic graphics switching
b. Put disks to sleep
Same exact issue. Running Catalina 10.15.1.
Reply on my own post :)
I've turned off true tone and my day is ending without this bug. I hope it will not come back again anymore
I turned true tone off quite some time ago. It does not seem to affect the issue.
Same here. Connect my LG UltraFine display via USB C and the monitor is at full brightness. Happens every time.
Same here. Why they don't care about this issue???
Too many people have this issue, where are you apple's support.....
I have the same issue with my MacBook Pro-16 and LG monitor.
I've the exact same problem. Am using a 2014 Macbook Pro 15" on Catalina 10.15.1
Same issue. Catalina 10.15.2. MacBook Pro 16". LG monitor.
Same here. Using 16" MBP with LG and older Cinema Display. Each screen takes turns going to max brightness after sleep. Latest everything installed. Using XRite iDisplay Studio to calibrate.
MacBook Pro screen goes full brightness
