Since Parallels 10 the monitor only in fullscreen modus is much brighter than before

and this "http://www.maketecheasier.com/disable-auto-brightness-adjustment-in-windows-8-1/" doesn't help. Any other ideas?

Thx
Ingolf

 

PD10 allows Windows to control display gamma in full screen mode. It's likely that gamma settings in your VM were adjusted making it look brighter.
You can either disable VM Configuration > Options > Full screen > Allow Windows to set display gamma option (VM needs to be shut down for that change) or reset Windows gamma settings: http://windows.microsoft.com/en-us/windows7/calibrate-your-display.