Trombone Shot

The trombone shot is a combination of the tracking shot and the zoom, coupled with the added difficulty of keeping focus.
With the camera mounted on a track and dolly, and the subject stood still, the camera begins to zoom in on the subject as it is pulled backwards on the track, all the while maintaining perfect focus on the subject. At a pre-determined spot the camera stops zooming, the grips stop tracking back and the focus puller stops rotating the focus ring. The difficulty is getting the speeds of the backwards-track and the zoom-in to match enough to create the effect, which is for the background to deepen in perspective (stretch, or drop away) while the subject remains the same size in frame.