Younger film fans are probably at least dimly aware that special effects compositing using chroma key techniques like blue screens existed in an era that predates computers. 1977’s Star Wars put blue screen techniques on the map in terms of popular consciousness, but variations on the matte process for combining image elements in film date back to the early 20th century, as Tom Scott nimbly explains in this short video chronicling how “green screen” worked before computers. It’s a taut little intro to the history and methods of a now-ubiquitous (and often invisible) part of the filmmaking process.