Question: what shade of green does a green screen have to be

title: Chroma key
text: Petro Vlahos was awarded an Academy Award for his refinement of these techniques in 1964 . His technique exploits the fact that most objects in real - world scenes have a color whose blue - color component is similar in intensity to their green - color component . Zbigniew Rybczyński also contributed to bluescreen technology . An optical printer with two projectors , a film camera and a ' beam splitter ' , was used to combine the actor in front of a blue screen together with the background footage , one frame at a time . In the early 1970s , American and British television networks began using green backdrops instead of blue for their newscasts . During the 1980s , minicomputers were used to control the optical printer . For the film The Empire Strikes Back , Richard Edlund created a ' quad optical printer ' that accelerated the process considerably and saved money . He received a special Academy Award for his innovation .