Windows Brightness issue after the 1809 update

Looks like the only fix right now might be to uninstall the 1809 update. Here's how:

To check what version of Windows 10 you have:

Win+X > System > At the bottom under Windows Specifications, next to "Version"

To uninstall the 1809 update: (Note, this uninstalls any programs and rolls back any credentials or settings changed since the update) 

 Start menu > Type "Recovery" > Click "Recovery options" (not "Recovery") > Under "Go back to the previous version of Windows," click "Get started" > Answer the prompts if you want, click "Next," then say "No thanks" to Windows Update, then "Next" again. After a restart, verify it worked by checking the version again. As long as it says something other than 1809, you should be good.

As far as I know, Windows is no longer pushing version 1809, so you won't be automatically "upgraded" after uninstalling it. You might get cumulative updates for your previous version, though, and it's safe to install these.

It did not solve the problem

I have the same problem on two ASUS laptops. I noticed it immediately the first time the laptops rebooted after the update. The reset already occurs during booting. Every time I start or restart a device, I have to reset the brightness to 100%. I use only one powerplan which is set to maximum power, and all battery saving options are OFF. (both laptops work mainly on net power, not the battery).

The 'display' options in 'advanced power options' have been removed in an earlier update;  you only have these if you started with version 1507. If you freshly install any newer version, you have a greatly reduced number of 'advanced power options'. I still have the options on my older laptop, bought before July 2015, but not on the laptop bought in 2016, which came with version 1511.

(Any Microsoft customer service rep should know this).

October 9, 2018—KB4464330 (OS Build 17763.55) 

Might be to early to say but after this update today and rebooting a couple of times the brightness has stayed at 100% both my laptop and workstation desktop.

KNOCK ON WOOD

It might be you're right, @JeffSchaffer --

For me, no fix from the Tuesday updates immediately, not on a subsequent shutdown and re-start.

But after Win10 had run from boot with the upgrade in, then four or five shutdowns and starts following this have come up in normal brightness.

I'm beginning to trust it, though I had a proper brightness a time or two while the problem was still lurking, before the upgrade.

Tricky, and it needn't be, if the Microsoft persons weren't so frightened to ever come out and say something about faults and fixes. It's not a grown-up attitude, and because of it, you could find it hard to respect them as they'd probably appreciate.