Green screens allow subjects to be superimposed on virtual backgrounds through a process called keying, where a single color like green is isolated and made transparent so another image can show through. Green is commonly used because people are unlikely to wear green clothing. To use a green screen, one needs a green screen, smooth lighting from different angles to avoid shadows, and no creases in the screen. Footage is imported and a chromakey filter applied to offer adjustment options for isolating the green from the subject.