 right|thumb|a computer generated representation of a dolly zoom. thumb|a frame from an animation showing a dolly zoom being performed. at the top of the image is the camera's view; the cubes stay the same size as the teapots in the background grow bigger. at the bottom of the image is a plan view showing the camera moving back while zooming in, illustrating how the effect is achieved. (click on the image to see the full animation.) the dolly zoom is an unsettling in-camera effect that appears to undermine normal visual perception. it is part of many cinematic techniques used in filmmaking and television production. the effect is achieved by zooming a zoom lens to adjust the angle of view (often referred to as field of view or fov) while the camera dollies (or moves) towards or away from the subject in such a way as to keep the subject the same size in the frame throughout. in its classic form, the camera angle is pulled away from a subject while the lens zooms in, or vice-versa. thus, during the zoom, there is a continuous perspective distortion, the most directly noticeable feature being that the background appears to change size relative to the subject. the visual appearance for the viewer is that either the background suddenly grows in size and detail and overwhelms the foreground, or the foreground becomes immense and dominates its previous setting, depending on which way the dolly zoom is executed. as the human visual system uses both size and perspective cues to judge the relative sizes of objects, seeing a perspective change without a size change is a highly unsettling effect, often with strong emotional impact. the effect was first developed by irmin roberts, a paramount second-unit cameraman, and was famously used by alfred hitchcock in his film vertigo. == alternative names == a dolly counter zoom is also variously known as: *the "hitchcock zoom" or the "vertigo effect" *"hitchcock shot" or "vertigo shot" *triple reverse zoom *reverse tracking shot *back zoom travelling *retrograde zoom *"smash zoom" or "smash shot" *vertigo zoom *a "jaws shot" *a "zido" *a "zolly" *telescoping *trombone shot *push/pull *the long pull *the trombone effect *a stretch shot *reverse pull *more technically as forward zoom
Cinematography Film_techniques Special_effects