This is a very easy camera trickery move to pull off. Very effective for a transition between rooms in a swift motion. Track back through an open door, then re shoot with the door shut and have the lens right up against the door, then track back. Through editing add a cross dissolve and it appears the camera fades through a shut door.
Above are two trombone tests shots. The trombone shot was originally invented by Alfred Hitchcock in his movie Vertigo when the protagonist looks down the spiral staircase. This is a great technique where you dolly zoom in while steadily zoom out on the camera. This shot is intended to create a sense of discomfort and disorder.
