The Huffington Post

moviefone:

There’s also his gradual shifting of camera angles and lens focal lengths to ratchet up the tension. At the beginning of the movie, the camera shoots the men from above; during the middle, it’s at eye-level; and late in the movie, it’s at table-level, looking up. This allows the actors to become increasingly dominant as the film progresses, even while enhancing claustrophobia by making it look like the ceiling is pressing in on the characters.

“12 Angry Men” at 55: Why Sidney Lumet’s Claustrophobic Classic Still Matters