Using the Green Screen

• What is a Green Screen?

A green screen is a background of solid colour (green and blue being the most common) that separates a subject from the background.

Chroma Keying was often known to use a blue backdrop in the past, but it has since changed to green being the most popular colour used in order to create transparency within shots. The reason for green being used as backdrops is because the green pigment isn't found in different skin tones. This is important because in order for Chroma Keying to be as effective as it can be, what you want to keep (the subject) and what you want to be removed or replaced (generally the background) need to have a distinct difference in colour.

Therefore, using the colour green allows the difference between the two parts of the shot to be kept distinct and separate from each other.

• How does it work?

It serves to separate the foreground from the background to allow for the background to either be rendered transparent or filled with the appropriate background or effects during editing. Using a green screen allows the original background to be rendered transparent.

• Think of a one minute scene that you could make using the green screen.

A weather forecast - using a green screen to superimpose the weather report behind the actor.

A fight scene - green screens can allow different background to be added in for scenery, but also for extra effects to be added to a scene, such as explosions.