This happens during the final level of the Elven campaign. The battle screens are too bright. It happens for all battles, and is very annoying.

I've googled and only found people reporting similar problems:
http://forums.ubi.com/showthread.php/252509-Weird-Graphics-Bug-Forums
http://heroescommunity.com/viewthread.php3?TID=18024&PID=822865#focus

But no solution.

I checked youtube videos, and some have bright battles, while others don't. But... what I noticed is that those with normal battles also have "night-time" on adventure map. In fact this post
http://heroescommunity.com/viewthread.php3?TID=22965
and this walkthrough
https://www.celestialheavens.com/viewpage.php?id=586
suggest the game is supposed to be played at night.

Any suggestions on how to fix this?