As many of us know, the Intel HD graphics power saving feature can cause the somewhat annoying automatic screen brightness adjustment, so I have disabled the option.
However, the automatic brightness adjustment can still kick in after the following usage pattern:
1) I am using the laptop on battery power
2) I hibernate the laptop
3) I plug in the laptop while it is still in hibernation
4) I wake up the laptop from hibernation
5) Now the automatic brightness changing can be perceived, despite the power saving feature being disabled in the Intel HD Graphics Control Panel
After this, I can fix the problem by unplugging and plugging again the laptop while it stays turned on.
So I suggest that there is still a bug somewhere which does not set the state of the power saving feature correctly in the described scenario.
This is an Optimus laptop (Acer V5-573G) with i7-4500U CPU and Nvidia GT750M.
