(updated 5-5-2015) I tweaked this mod for myself, but since I saw a few people requesting this kind of mod I decided to post it online.
I did not make the mod myself, I just altered some settings. To create the effect I wanted, I used the SweetFX preset of K-Putt.

Basically what this mod does, is making nights way darker. (screenshots look slightly darker then in-game).
I also tried to make lights a little brighter, in this way players are happy to have flashlights on their guns, with the headlights of the vehicles and lights at the landingstrips. Thunder will look absolutely stunning, and you could watch at the citylights for hours.
Ajust your game brightness to your own likings, I prefer having it all the way down.
If you want to use the darker nights in an other preset, just copy the setting from levels and liftgammagain (and maybe bloom, if you want to).

To enable the mod ingame: press f12.


-update: many people asked me to make it brighter, so thats what I did. It still is pretty dark, but you can see more things without needing your lights. But when its raining, or when you are in a plane the game will still be very dark. Also: I changed some more stuff, so the fps drop will be way less.

k-putts preset: https://www.gta5-hub.com/misc/reshade-sweetfx-graphics-mod

If you want to download the previous, darker version: http://www.gtainside.com/en/download.php?do=detail&main_cat=599&start=24&id=72320&orderBy=