What lights are used for night portraits?

I have been seeing many friends asking about the shooting of portraits at night. A large part of the situation is: I want to use city lights as the background, if I don't use flash, my face will be black; If you use a flash, the background will be very dark. The simplest solution is to synchronize slowly with the flash. I simulated three situations (of course, the exposure time here is a little too long for taking pictures, just to show the different effects of the flash): 1. There is no flash (10 second), the background is bright enough and the face is black (if the face is just right, the background is too violent).

2. The general usage of flash (1/60 seconds synchronization), the face is just right and the background is dark.

3. Synchronize slowly with the flash (8 seconds), and the face and background are just bright, retaining a little warm tone of ambient light.

When the flash is used for slow synchronization, even a slight movement will have no effect, but a fantastic effect will appear. Better use a tripod.