Movies are often filmed on location, though this can be a complex and expensive process; streets need to be blocked off, permits need to be acquired, and so on. TV shows often can’t afford outdoor location filming, in terms of both time and money. On the other hand, there are outdoor shots in lots of TV shows; how do they do it? The answer is the extensive use of blue and green screens, which are replaced in post-production by realistic backgrounds. This is sometimes called the “virtual backlot”, as illustrated in this great demo reel from Stargate Studios:

Most of these blue/greenscreen effects are imperceptible to the viewer: everyday shots like two characters walking down a city street, or a character talking on their cell phone in front of a city skyline. Most of these shots are from TV shows that aren’t associated with flashy effects, like medical shows, law-and-order procedurals, and family comedies. I was especially impressed by the clip from Ugly Betty starting at about 2:12; hardly anything in this scene was “real”.

Here’s a longer look at the effects Stargate did for ABC’s Revenge, a lot of which takes place in houses near the ocean. In many cases, the camera isn’t moving much, which makes the problem easier, but there are a couple shots that follow characters as they walk around a wrap-around porch that I thought were particularly impressive, starting at about 1:44 and 2:14:

In this case, some matchmoving is probably involved, as opposed to the pan/tilt shots where one can get away with different views of a spherical panorama. Keep in mind that these effects need to be turned around by the VFX company in a week (or less), so there isn’t that much time to polish the tiniest details like wisps of hair.

Post Magazine has a great article on the types of visual effects involved in last season’s new TV shows — not just bluescreens for background replacement but more advanced work like changing the season of a shot or adding CGI creatures.