Many movies contain a scene that is portrayed as taking place during the night. Due to the low amount of light some tricks are applied. Unfortunately, I couldn't find much info on this. To me it seems a lot of night scenes make use of so-called "black lights". These lights give lighter surfaces some sort of purple glow and thus enhance the visibility of lighter surfaces while the darker parts of the scene remain dark. For example here is a shot from Terminator 2:
It clearly has the typical purple glow to it, but it's more subtle compared to the use of only a blackight. Therefore I was wondering whether black lights are used (in combination with normal lights), do they use another kind of lights, or are most night scenes (digitally) edited afterwards?