In the early days of film, scenes would be staged in a theatrical sort of tableau, with the camera stuck in one spot and characters moving around the frame. This is called a master shot - it includes all the geography of the scene. And while that's still a good way to stage things for many purposes, filmmakers quickly discovered that cutting between different perspectives - eg moving from a wide shot to successively more intimate closeups, that mirror the intensity of the characters' emotions. This is called coverage. Watch any film with the sound turned off and you'll be struck by how many scenes just consist of someone's face looking off the left or right of the frame.
But that means a whole bunch of extra decisions about where to put the camera - which are the director's job to decide. If you mess those up, viewers will get confused about the interior geography of the scene, who's looking at whom etc.; you see me looking like this: (o < o), then I show something else, then you see me looking like this: (o > o) - you naturally assuming I'm looking at a third thing that's off to my left. Why?
In any scene there's a primary character and the object of his/her attention - usually another character, but maybe an object or even an imaginary point in space. The line between the main character's eyes and the object of their gaze is called 'the line of interest'. So when you're placing the camera, you need to pick one side of this line for the master shot and stay on it for all the coverage. It's also called the 180 degree rule, because that line would split an imaginary circle into two halves of 180 degrees each. That way when you cut between different actors, they're always facing in more-or-less the same direction and the viewer intuitively knows where everyone is. There's also a 30-degree rule which says that successive cuts should involve a change of at least 30 degrees (relative to the midpoint of the line of interest) so as to avoid the sensation of a 'jump' - a movement so minimal that the brain is more inclined to scribe it to a missing bit of footage than a real change in perspective. Of course that can be (ab)used for artistic effect.
If there are more than 2 people in a scene then there can be multiple lines of interest, but there is only ever one at once. If you want to move to a different one, you need to establish the new line. You could pan the camera, follow one of the characters as they walk into or out of the frame, pivot by showing three characters and then cutting across a secondary line when the third person talks, and so on.
Camera angle choices are the biggest part of the director's job during production, and probably the most stressful, because a) every new camera angle requires, on average, at least an hour of additional work for the whole crew, and b) they define the style of a film, from amateurish to visionary - and while audiences can be tricked with the magic of editing, the actors and crew can generally read the director's level of skill during shooting and will respond accordingly.
You know, I bent terminology a bit here - strictly speaking, a master shot could involve substantial movement of the camera - a classic example is the incredible opening sequence of Welles' Touch of Evil. It's more true to say that a master shot encompasses all the action and could play on its own...but a lot of the time, the master ends up being a static shot that's staged in depth.
But that means a whole bunch of extra decisions about where to put the camera - which are the director's job to decide. If you mess those up, viewers will get confused about the interior geography of the scene, who's looking at whom etc.; you see me looking like this: (o < o), then I show something else, then you see me looking like this: (o > o) - you naturally assuming I'm looking at a third thing that's off to my left. Why?
In any scene there's a primary character and the object of his/her attention - usually another character, but maybe an object or even an imaginary point in space. The line between the main character's eyes and the object of their gaze is called 'the line of interest'. So when you're placing the camera, you need to pick one side of this line for the master shot and stay on it for all the coverage. It's also called the 180 degree rule, because that line would split an imaginary circle into two halves of 180 degrees each. That way when you cut between different actors, they're always facing in more-or-less the same direction and the viewer intuitively knows where everyone is. There's also a 30-degree rule which says that successive cuts should involve a change of at least 30 degrees (relative to the midpoint of the line of interest) so as to avoid the sensation of a 'jump' - a movement so minimal that the brain is more inclined to scribe it to a missing bit of footage than a real change in perspective. Of course that can be (ab)used for artistic effect.
If there are more than 2 people in a scene then there can be multiple lines of interest, but there is only ever one at once. If you want to move to a different one, you need to establish the new line. You could pan the camera, follow one of the characters as they walk into or out of the frame, pivot by showing three characters and then cutting across a secondary line when the third person talks, and so on.
Camera angle choices are the biggest part of the director's job during production, and probably the most stressful, because a) every new camera angle requires, on average, at least an hour of additional work for the whole crew, and b) they define the style of a film, from amateurish to visionary - and while audiences can be tricked with the magic of editing, the actors and crew can generally read the director's level of skill during shooting and will respond accordingly.