Editing Compositing (section)

== Physical compositing ==

In physical compositing the separate parts of the image are placed together in the photographic frame and recorded in a single exposure. The components are aligned so that they give the appearance of a single image. The most common physical compositing elements are partial models and glass paintings.

Partial models are typically used as set extensions such as ceilings or the upper stories of buildings. The model, built to match the actual set but on a much smaller scale, is hung in front of the camera, aligned so that it appears to be part of the set.  
Models are often quite large because they must be placed far enough from the camera so that both they and the set far beyond them are in sharp focus.<ref>Professional Cinematography, Clarke, Charles G., A.S.C., Los Angeles, 1964, p 152 ff.</ref>

Glass shots are made by positioning a large pane of glass so that it fills the camera frame, and is far enough away to be held in focus along with the background visible through it. The entire scene is painted on the glass, except for the area revealing the background where action is to take place. This area is left clear. Photographed through the glass, the live action is composited with the painted area.  A classic example of a glass shot is the approach to Ashley Wilkes' plantation in ''[[Gone with the Wind (film)|Gone with the Wind]]''. The plantation and fields are all painted, while the road and the moving figures on it are photographed through the glass area left clear.

A variant uses the opposite technique: most of the area is clear, except for individual elements (photo cutouts or paintings) affixed to the glass. For example, a [[Ranch-style house|ranch house]] could be added to an empty valley by placing an appropriately scaled and positioned picture of it between the valley and the camera.