Quick Answer: Whip pans are intentionally sloppy shots designed to be abrupt and disorienting. As several films have shown, these shots can be used as an unbroken means of transitioning between two shots, to indicate the passage of time, or to create an atmosphere of frenetic energy or disturbance.
Whip pans are intentionally sloppy shots achieved by literally "whipping" the camera. They refer to a motion so abrupt and disorienting, the camera's lens can’t keep up with the movement, resulting in blurred lines and indistinct photography. These types of shots can be used as an unbroken means of transitioning between two shots, to indicate the passage of time, or to create an atmosphere of frenetic energy or disturbance. They also make for tremendously poor screen shots.
The opening sequence of Hot Fuzz (2007), a narrated montage which explains Simon Pegg’s character’s quick and decorated rise through the ranks of his police force, uses constant whip pans for transitional purposes. They facilitate the movement of his accolades from one to the next, changing setting with each whip.
Hot Fuzz uses whip pans heavily throughout, often for comedic effect, going so far as to accompany them with an audible “whooshing” sound.
Using a whip pan to transition between settings requires the use of a whip cut, which involves editing together two separate whip pans into one seamless effect. This is possible because of the blurred image – the viewer’s eyes and brain cannot detect the edit amidst the blur.
Director Paul Thomas Anderson utilizes a good deal of whip pans in his films Boogie Nights (1997) and Magnolia (1999). In both pictures, the whip pans both serve as a transitional trick, and also add to the energy and atmosphere of the scene.
This contrasting example, from Cloverfield (2008), is used entirely to build frenetic energy and is not used as a transitional piece.
Whip pans are not a new trick. A famous classic example comes from Some Like it Hot (1959), where the scene of Monroe and Curtis kissing whips to another scene.
Plus, its dizzying quality seems a fitting way to move from kissing Marilyn Monroe.
Another example of whip pans in use, the Brian De Palma film Snake Eyes (1998) presents the first 12 minutes of its runtime as one long, continuous take, through cinematic trickery facilitated by whip pans and whip cuts. The scene is actually comprised of many shots put together which are fused by the whips.
The whip pan certainly has its place in the language of any cinematographer, and can be used to craft clever shots. It can be overused or employed ineffectively, but when done correctly (or for comedic effect), the whip pan is a solid tool.