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ELI5: How Do They Film TV Shows/Movies That Take Place in Big Cities?

When they're making TV shows that take place in Chicago or LA or New York City, how do they film on the streets?  Do they just film around people, or do they block off the section they want to use?  They can't just shut down part of a city to film there, so how do they do it without getting interrupted?
gpt
- For TV productions, sometimes sets are built that look like an actual street. They're then reused over and over, with minor changes (like rotating store windows) to keep them looking fresh. This is what you saw on Seinfeld, and on movies that have really elaborate street scenes like Back to the Future. (If you ever get the chance, try to visit one of these sets. They're eerie, because they're incredibly detailed and real-looking yet everything is empty and built into walls. Feels like an episode of The Prisoner or something.)

- For high-budget productions, they'll actually pay the city to shut down a block or two for a while. This is expensive as hell.

- In recent years, it's become more common to send a skeleton crew to a city centre -- just one camera, no sound equipment, little to no lighting, bare minimum personnel -- to shoot a 'plate'. They just shoot scenes in the city, 10 minute segments of footage at key locations, with nothing in them, no performers. Then the actors perform their scenes in front of a green screen and are digitally composited onto the plate. This is a lot cheaper than actually shutting down blocks to keep performing scenes, because that tiny crew can shoot the plate quickly, easily, and cheaply without interfering with other people. You'd be surprised just how common this is for non-special-effectsy shows like 30 Rock and Ugly Betty.

- If your show has a *ton* of outdoor content, you pay to shut down blocks and streets -- but you do it in a much smaller cheaper city/town, and edit in aerial shots of the city you're *pretending* to use. Psych, for example, is set in Santa Barbara, USA but is actually filmed around Vancouver and other British Columbia, CAN towns. They sent a helicopter to Santa Barbara, filmed an hour of aerial footage, and just splice it in a few times an episode to make it look like they're in the USA. (If you ever watched The X-Files, they shot the first half of the series in small Canadian towns and the second half in Los Angeles, which is why there's a sudden stark shift from overcast gloom and foggy villages to sundrenched suburbs about halfway through.) It's a hell of a lot easier and cheaper to shut down a few blocks in Ashcroft than to shut down 5 metres of Brooklyn.