Forced perspective is a filmmaking technique to make larger objects appear smaller to the viewer or vice versa, depending on their relationship to the camera and each other. Forced perspective is used primarily to make objects appear far away when set space is limited. Movies (especially B-movies) in the 50's and 60's are notorious for obvious and badly done forced perspective angles.

Example 1

Imagine a scene in an action/adventure movie in which dinosaurs are threatening the heroes. Cloning dinosaurs can be costly and dangerous; making a miniature model of a dinosaur is something anyone can do. By placing a miniature model of a dinosaur close to the camera (and possibly making the model blurry), the dinosaur may look monstrously tall to the viewer, even though it is just closer to the camera.

Example 2
Imagine another scene in which two characters are supposed to be interacting in the foreground of a vast cathedral. Instead of actually filming in a cathedral, the director mounts a large painting of a cathedral's interior in a studio and films the actors talking in front of the painting. This gives the effect on film that the characters are in the foreground of a large room, when in reality they are standing next to a flat surface.

These are rather extreme examples of a technique that is often moderately used in cinematography. The Lord of the Rings is a popular movie that employs an almost constant forced perspective. The character of Gandalf is always filmed slightly so, giving the impression that he is taller than the actual height of actor Ian McKellen. Smaller humanoid races were also frequently filmed in this manner, to make them appear smaller.

See also: perspective distortion