Compositors do ‘chroma keying’ (also just called keying). This is where they select a specific part of an image that has a distinct color or lighting and extract it to be used elsewhere. This method is commonly used with ‘green screen’ or ‘blue screen’ footage, where a subject has been shot in front of a singularly green or blue background, to be able to place the subject in a different setting or environment later, in post-production.

Compositors work as the last part of a VFX 'pipeline’ (the name given to the VFX production process).