Someone asked me recently how to shoot day for night and I thought I’d post my response here:
1. What you’re looking for is contrast, so it’s really only possible to make it believable if it’s sunny. Cloudy is more difficult.
2. If you must include the sky in a shot, use a polarizer to darken it. The biggest giveaway is a sky that’s brighter than the subject and terrain (see any 50s or 60s widescreen epic).
3. If at all possible, don’t include the sky in any shots or only include it in an establishing shot where only simple shapes are outlined in the sky (like the tops of buildings). If you make this a static shot, it will be easy to darken the sky in post.
4. Shoot when the sun is at a low angle, if possible (early morning or late afternoon). Keep the sun to the back of the subject(s) and off to the side a bit whenever possible and expose for the highlight, making the face underexposed, but retaining a bit of detail so you have some flexibility in post. It’s easier to get rid of shadow detail than to bring it back.
5. Color – Some people say to white balance to tungsten so everything is blue. I think it’s better to keep your white balance correct (daylight for daylight) and then play with color in post. The main thing that distinguishes night in my mind is desaturation. Then a slight shift towards green and blue. But more important than that is that you match whatever night looks like in the rest of your film. So if you’re showing night as blue, then do the same in your day for night shots.
While it would be great to have your day for night scene look exactly like a “real” night scene, if the action of the scene is important and involves the viewer, it won’t matter as much how perfect it looks. There’s quite a bit of mediocre day for night footage in Pan’s Labyrinth, for instance, but it doesn’t really matter because it fits the style of the film and the viewer is invested in the action.
There are a lot of differing opinions on this subject, I’d encourage anyone who’d like to learn more to do some research. cinematography.com is a good place to start.