Compositing is the process of blending multiple video elements in a single image. Video editors can select the sky from one image, a background from another and a character from a third, and add these elements together to create a scene. One of the most common types of compositing is green screen--or blue screen--photography. This involves shooting an actor against a brightly colored screen, then digitally removing the color and adding another image to serve as the background.
CGI, or computer generated imagery, occurs when computer animators produce images that a video editor then inserts into a live-action image. The computer generated images can be anything from birds in a distant sky to an explosion or even a fully animated character. Some Hollywood action and science fiction films include scenes that use more CGI than actual photography--the scenes are manipulated on video before being printed to film for theatrical distribution.
Video transitions are useful in every type of video. Home movies can feature fades or dissolves to make transitions from one scene to another smooth and natural. Other common video transitions include wipes and the iris, in which a growing circle gradually reveals or conceals the on-screen image.
Video editing programs make it easy to add text as a composite layer over an existing image. This is the technique videomakers use to add titles and credits to a movie or to produce subtitles that accompany a translated foreign film.
Videomakers and editors frequently employ video color correction to change the look of individual scenes or entire movies. Color correction alters the tone, hue and color saturation of a video image. This can make a scene shot during the day appear to occur at night, by darkening the colors and adding a blue tone. Color correction can also adjust for the differences in color temperature between sunlight and artificial light, which the human eye can adjust to but cameras display as drastically different.