Installed Kubuntu 16.10 Beta 2 that comes with Plasma 5.7.5 and there screen goes infinitively brigher if there is no moving things on screen e.g. cursor. Happens with both Intel and Nvidia cards and their latest drivers. Reproducible: Always Steps to Reproduce: Already login screen has this problem.
I've not seen any other reports of that. Are you sure you don't have any extra software you've installed running.
This happens already in live session before install.
In final release of Kubuntu 16.10 this does not happen anymore.