Where would Superman be without the red flutter of his cape, the yellow light of Earth’s sun—and the green screen behind him? The green screen never makes it into the movies, of course; it’s replaced by a sky full of stars, or the skyline of Metropolis. For more than a century, filmmakers have been using the “green screen” technique—or, to be precise, chroma key compositing—to allow us to believe that their actors are doing the impossible. That they’re soaring above the Earth, or investigating a crime in Toontown, or assembling the Avengers, or encountering a T. rex.
