Okay Frank, thanks. I read about this last week and I didn't understood much, but somehow I manage to find the right settings after I found some tips from a member ParoXum, using KAM's VertexPaint.
This are the most default settings for the game.
Nightime between 45-50
No need to paint, just export after the settings are made. Depends now how I use the settings because some buildings are having a little bright and dark so I need to test a few time before I hit the right sport. For those that are having trouble with this, now you know. You can check by using two Med Editors in order to reach the right settings, one game with original stuff and the other one modify Vertex.