I can see from searching on Google, there's a lot of people with similar issues, even using other brands (HP, Lenovo).
Just to make it clear about the way I use my laptop:
When i'm moving away from it, I press the power button and it instantly goes to sleep (screenshot of "Power button" settings -
http://i.imgur.com/OexfGSo.png ).
When i come back, i turn it on, and that's when the screen brightness is dimmed
😞TLDR: When pressing power button, computer goes to sleep (with full brightness), awakes with screen dimmed.BUT:If I close the lid, the computer goes to sleep, and when i open the lid again, it turns back on with the Screen brightness as it was! It does not get dimmed this way. It works as it should.