Green screen, also known as chroma key technology, is best known for bringing amazing special effects to the movies. Green screens can help create many scenes, from superhero battles to a more mundane city scene outside a character’s window. But how long have green screens been used, and how has the technology changed? Here’s a breakdown of the evolution of the green screen.
The Early Days of Special Effects
Screens were used to produce special effects even back in the days of the theater. Backdrops could be painted on curtains and dropped behind the actors to give the impression of time and place. When movies came into vogue, directors and cinematographers experimented with different techniques to create similar backgrounds and effects. At first, directors used double exposures. They blacked out parts of a set, ran the film through the camera again, and thus recorded new footage on the blacked-out parts—an example of this effect is the fields rushing by a window in the 1903 film The Great Train Robbery. But the use of black screens could only do so much.
With the arrival of color film, more effects became possible with blue screen. Actors performed in front of a blue-colored screen. Then they filmed another scene and laid the films atop each other, producing special effects like flying, invisibility, and more. A famous early film that employed blue screen was 1940’s The Thief of Bagdad, showing a genie escaping a bottle, a flying carpet, and more. Filmmakers continued to use blue screen for decades afterward. Later, computers took over the physical overlaying process, as with the film Who Framed Roger Rabbit? and the Star Wars film The Empire Strikes Back.
Blue screen was the preferred method for filmmakers for a very long time, though they used green screen on occasion. Briefly, the Walt Disney Company used a technique called the sodium vapor process, also referred to as “yellow screen,” which employed a special camera. The resulting footage could be blended with a background matte. The most famous film to use yellow screen is Mary Poppins (during the penguin waiters and other live-action/animated sequences). The last film to use yellow screen was Dick Tracy in the 1990s—the technology eventually petered out.
Green screen came into greater use with the advancement of digital cameras and editing software, so now most studios are painted or appointed with that shade of green. Digital cameras gather more information on the green part of the spectrum. Green screens are also much easier to light than blue and reflect more natural light from the colored walls and green screen floor. Most software with chroma key editing features also default to keying out green color. In short, in the evolution of the green screen, the technique became the standard.