My Fn key doesn't seem to work/help me to adjust brightness. So I tried to minimize the brightness (inside the Control Panel). To my surprise, the screen went entirely black and I couln't see a way to cancel it. Now I can't do anything in my area, not even log on to the account (it seems). The only thing I can do is to enter Windows' Security Mode. There, I see an option to log in and I can enter a security version of my area and there I have proper brightness. If I try to enter with Windows "normal mode", I can't even see the login screen.
I tried from my account in Security Mode using powercfg and update the brightness value. However it doesn't seem to have effect on Windows' Normal Mode.
Any suggestions on what I can do?