In visual effect post-production, compositing refers to creating complex images or moving images by combining images from different sources - such as real-world digital video, digitized film, synthetic 3-D imagery, 2-D animations, painted backdrops, digital still photographs, and text.

Compositing is used extensively in modern film to achieve effects that otherwise would be impossible or not cost efficient. One common use for Compositing is digital scene extension which enables film makers to shoot on a relatively small set and create the impression of a significantly larger set by adding additional scene objects digitally.

Today, compositing generally involves the use of computers, however in the past, compositing was often done using optical tricks. In many movies, studio scenes were extended using Matte paintings which were created by an artist and then combined with live-action footage.

In feature film, movies are generally shot on 35mm film. For compositing, the film has to be digitized with a film scanner. It is then transferred to a computer where it can be edited. The compositors gather all material they need for a scene and then combine the different clips to achieve the result that they need.A technique that greatly facilitates compositing is bluescreen where an object or actor is filmed in front of a solid color screen. During compositing, all areas of a frame with that color are removed which allows the compositor to place the object or actor in front of a new background.this is usually seen in the tvprograms now a days.

In professional film making, special servers and workstations are used for compositing. On a smaller scale however, it is possible to achieve similar effects using just a state of the art home computer. Software like Adobe After Effects has many of the features you would expect in a professional compositing software.