Green screen compositing is also known as “Keying” or “Chroma Keying.” It is used to delete the green recorded background of a video taken in front of a green screen and replace it with another background of video. This technology is used in TV shows, news broadcasts and feature films.
- After Effects offers very useful Color Key and Chroma Key tools that enable the editor to successfully remove the green screen. The editor selects a color to “Key” by clicking on that color on the screen. The editor then selects a percentage of similar colors to include in the keying. This accounts for variations in the color created by shadows or movement. After Effects offers a tool in its keying components that “Feathers” the “Key” to soften the edges of the actors.
The editor inserts the background into the video. The background must be of the same resolution as the original footage or it will look distorted. The background must also fit the level, or height, of the actors, otherwise the green screen compositing will not look real. Most professional productions storyboard and plan the background shots with green screening in mind so that the footage will fit perfectly with the actors.
Blending is an important part of green screen compositing in After Effects. The program offers several tools that help in blending the actors and the background. The “Adjust” tool and other color correction features allow the editor to match the video of the actors with the video of the background in terms of color. Typically the editor also blurs the edges of the actors slightly so their movements do not seem too sharp.
How to blend on after effects