The technique, also known as a dolly zoom, is actually rather simple in its design. A stationary object is photographed or filmed as the camera moves towards or away from it while adjusting its focal point so that the object remains the same size relative to the rest of the scene.
In the example from Vertigo above, Hitchcock accomplished the shots by pulling the camera away from the focal object while zooming in at the same rate.
You can also see the effect in action when employing a still camera here. French photographer Micaël Reynaud employed various-length lenses, from 24mm for the close shots to 84mm for the long-distance ones. It’s an awesome technique to add a sense of the emotional impact of a scene or just add a bit of confounding visuals. [Dolly Zoom Wiki via PetaPixel – Image: Peter Dunne / Getty Images]