Greenscreen
American engineer Petro Vlahos invented the modern color-difference traveling matte system that established electronic chroma keying and the green screen
The foundations of matte compositing began in Los Angeles when cameraman Frank Williams patented a traveling matte method in 1918. Williams filmed actors against black backgrounds to create high-contrast silhouette masks, allowing separate foreground and background elements to combine on an optical printer. In 1940, visual effects artist Lawrence9 Butler advanced the concept by using blue backdrops in Technicolor cameras for the fantasy film The Thief of Bagdad. Early color matting remained labor-intensive, often leaving harsh blue fringes and halos around moving subjects.
During the late 1950s in California, engineer Petro Vlahos addressed these fringing artifacts while working with the Motion Picture Research Council and Metro-Goldwyn-Mayer on the epic film Ben-Hur. Vlahos developed a laboratory method that separated the red, green, and blue color channels of film. He used mathematical difference formulas between the color records to extract transparent mattes that cleanly isolated fine details such as flying hair, smoke, and motion blur without edge halos.
Vlahos patented this color-difference method under US Patent 3,158,477 and later adapted the mathematics into real-time analog video hardware through his Ultimatte Corporation in 1976. While early film compositing favored blue backdrops to match film emulsion sensitivity, video production in the 1970s and 1980s shifted toward bright green. Green backdrops required less studio lighting, contrasted sharply with human skin tones, and matched the high sensitivity of digital camera sensors.
By turning the physics of color separation into a repeatable mathematical formula, Petro Vlahos transformed composite filmmaking from a trial-and-error optical trick into a seamless digital canvas.