Car at night
Simulator
Three sources, none of them allowed to be a lamp
A car interior gives you no room, no grid and no wall to hide behind, and the audience knows exactly which lights should exist: the dashboard, whatever the car is driving past, and nothing else.
The dashboard is motivation, not a key
It is real, it is in shot, and it comes from below the chin. Used alone it lights faces from underneath and the scene turns into a horror film. Keep it low enough to see and let something else do the work.
Streetlights say the car is moving
A sweep of warm light across the face every few seconds does more to sell a moving car than anything out of the window, which is usually a blur anyway. The rhythm matters: too regular reads as a machine.
The hidden unit does the lifting
A soft source on the bonnet, on the dash, or rigged outside the window. It has to be soft, low in level, and placed where a streetlight or the sky could plausibly have put it.
Watch the angle, not just the level
The giveaway is never brightness, it is direction. Light arriving from directly in front of the actor’s face, with nothing in the world to make it, is what tells an audience the scene is lit.
Windows are mirrors
Everything you put in the car is reflected in the glass, including the crew. Polarisers, black cloth and careful angles do more for a car interior than any lamp.
Process or poor man’s
Shooting static against a screen gives you control and costs believability; towing the car gives you real passing light and costs everything else. The lighting problem is the same either way.