Shoot day exteriors with ND filter and underexpose to fake night — cheaper than night shoots. Requires precise metering or looks phony.
You're shooting a night scene, but only have two hours of daylight and a budget that doesn't allow for real night setups — this is where you turn to the American Night. You shoot while the sun is still up, mount a strong ND filter (usually ND 3.0 to 4.8) in front of the lens, and deliberately underexpose by two to three stops. The result: daylight becomes diffused twilight, shadows deepen, and the sky turns bluish-gray. Quick, efficient, and the crew isn't standing on a dark corner at 10 PM.
In practice, this only works if you maintain the balance. Too much ND and too little underexposure looks like pale midday through a filter. Too little ND and the sun is still visibly above the horizon — immediately recognizable, immediately unbelievable. Additionally: the contrast must be right. Without additional key light (often an HMI or Fresnel), the scene looks flat, as if shot underwater. So you still need a handful of reflectors or smaller artificial sources to model faces and maintain the sense of depth. Otherwise, you'll be in the edit and won't be able to see your actors' eyes anymore.
The crucial trick: the sky gives you away immediately. A real night has an almost black, textureless sky. If you're shooting at 2 PM and still see cloud details, even if they're dark blue, every viewer in the cinema unconsciously knows that a trick has been used here. Good colorists can correct this in post, but it costs time. Some DPs therefore prefer to shoot shortly before sunset, when the golden hour is over and the sky naturally darkens — then the American Night is less obviously a trick and becomes efficient lighting direction. With the right ND values and fill lights, you get a real night atmosphere without waiting for actual darkness.