What is the primary purpose of chroma keying (green screen)?

The primary purpose of chroma keying, often referred to as 'green screen,' is to remove a specific color (typically green or blue) from a video image and replace it with another image or video. This allows you to composite a subject filmed in front of a solid-colored background onto a different background, creating the illusion that they are in a different location or environment. The process involves identifying all pixels of the chosen color in the video and making them transparent, then layering the subject over the desired background. Chroma keying is widely used in film, television, and live streaming to create virtual sets, add visual effects, or place subjects in environments that would be difficult or impossible to film in reality. For example, a weather forecaster can be filmed in front of a green screen, and the green background can be replaced with a weather map, making it appear as though they are standing in front of the map. While other techniques exist for compositing images, chroma keying is particularly effective for creating seamless and realistic composites with minimal artifacts, especially when using well-lit and evenly colored backgrounds.