Night exterior

Simulator

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Edge over face 
Face against background 
Face level 
Key light quality

Night is read from the ratio between a cold edge and a warm source, not from how dark the picture is.

Try these
A scale in stops with the face, the cold edge and the background marked, and the bands each should fall in

Dark enough, visible enough

A night exterior has to be dark enough to read as night and bright enough that an audience can follow a face. The answer is never a level, it is the ratio between a cold edge, a warm source and almost nothing else.