Screen brightness is being reset to maximum after reboot

UPDATE: I tried this and it worked for me (so far).

1. turned off second monitor
2. unplugged the thunderbolt/display connection from back of iMac
3. manually put iMac to sleep (not letting energy saver do it)
4. main monitor woke up this am and… iMac screen did NOT reset to max brightness. Seemed to stay put.

While that is a PITA, it sure beats a 30-min calibration cycle daily.

Definitely some Catalina issue with 2nd monitor.

My machine is a Retina 5K late 2014 maxed out.

Thanks to others on here who have been posting clues. Helped me figure it was a 2nd monitor issue (well, a Catalina issue RE 2nd monitors). Hope Apple fixes this "feature." And no, this never happened before Catalina for me.

Same problem with my iMac. It resets to max brightness on the main screen perhaps 95% of the time, while leaves it at set brightness the remaining times. I have dual monitors. I thought the Power Nap fix below solved it, but alas, it did not.

silverlarry wrote:

Also, after sleep, keyboard repeats keystrokes. Sometimes a single keystroke will repeat it 5 or 6 times in a row with just a quick tap.

I have this same issue whilst typing sometimes part words or keystrokes repeat. I also have the issue with the screen reverting back to full 100% brightness when resetting or powering on. I have a imac 5k Late 2014 to fix the brightness I have to calibrate my screen every time I reset or reboot this is really not ideal!!

Yep. Same here. 5K iMac running 10.15.3

I **just** "upgraded" to Catalina and now screen goes to blaring 100% brightness after sleep at night.

This is a real problem because I use a CALIBRATED system for pro video & photo work. This means I have to calibrate every day. Two monitors with calibration daily… I lose about 30 min of work time every single day. This is a huge problem!

Any fixes?

I have "prevent computer from sleeping automatically when the display is off" checked.

I have "enable power nap" checked (but will try un-checking it).

Dunno. Next step is to turn sleep off forever. I just can't flush 30 min per day in calibration.

I am having the same issue. I think I may have found the cause, but not a solution. My iMac restarts at full brightness when I have a second monitor connected (regardless of whether it is turned on or not). When the second monitor is not connected, it starts at previous brightness setting.

If this is the case, it's a bug for Apple to address.

Ah, yes. I have two monitors also. Mine is a Dell. Saw lots of chatter about this being a problem with LG monitors or something. I thought it was a brand-specific problem. It might be (that would be Apple). I'll try disconnecting 2nd monitor and see if when I wake up machine and reconnect 2nd monitor it's kept brightness same. I'll report back.

YES. I updated to 10.15.4 and seems to have resolved the brightness auto-setting. Seems to have retained the monitor color profile too (using X-Rite Color Munki).

BUT … immediately following update, had about three spontaneous shut downs of the iMac. As in… went black and restarted with no warning. Lost all open files & projects. Was able to open last-saved version thankfully.

So… I'd suggest multiple restarts / reboots of your system and saving very often in the first day after updating. Could have been coincidence. But happened immediately following install of update and has never happened before (or since).

I have this problem as well when the laptop wakes up from sleep.

Same here.. up-to-date catalina (2018 high-end cto 15" macbook pro)

any solution?

PRAM, SMC reset did not help

Also, after sleep, keyboard repeats keystrokes. Sometimes a single keystroke will repeat it 5 or 6 times in a row with just a quick tap.

Did you find a fix for this? I have same problem on my iMac. Thank you.

I had the same problem.

Go to Energy Saver, unselect "Power Nap while on battery power". This might work.

Thanks, your solution works for me!

I have the same issue as well with my 2017 13" MacBook Pro's. My work laptop as well as my personal one. I already have 'power nap' unselected, but the issue persists. Both are Catalina 10.15.2.