Canting is a compositional technique you can use when you want to convey that something is wrong to the audience. It’s conventional to frame up shots with a level horizon. Canting the camera ever so slightly to the left or the right can help to convey a sense of disequilibrium and unease to your audience.
Examples of canting
The example of canting used here comes from Scream (Wes Craven, 1996). Talking to a mysterious caller on the telephone, Casey Becker (Drew Barrymore) asks why he wants to know her name. “Because I want to know who I’m looking at,” he says. Craven uses canting in this shot to underscore the sense of unease felt by the character.
If you want to see some other great examples, check out the climatic scene of Thor (Kenneth Branagh, 2011) as the title character, portrayed by Chris Hemsworth, faces off against a giant, metal automaton controlled by his brother Loki. Branagh uses a canted shot as Thor makes the decision to sacrifice himself.
In the opening sequence of 28 Days Later (Danny Boyle, 2002), this technique is used to convey a sense of dread as Jim (Cillian Murphy) explores a deserted London.
The Dutch Angle is an excellent master cut which looks at the use of canting throughout film history.