Vlahos died. But, he refined it and developed a way to minimize the unfortunate side effects of earlier methods, like the strange, unwanted glow that might surround objects. Glassware, cigarette smoke and hair blowing in the wind had been particular problems. But a complete list of his handiwork would be almost impossible to compile.
Vlahos held at least 35 movie-related patents, and as they expired, others in the industry put his discoveries to their own uses. Petro Vlahos was born on Aug. 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 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.
The footage of the actor could then be added to any background shot, such as a desert, a lunar landscape or the bottom of the sea. Using different lenses when shooting the matte footage and the background shot, the directors of the movie, The Thief of Bagdad , were able to turn actor Rex Ingram into a gigantic genie. While Butler pioneered the art of compositing, his technique also had its own limitations and was not able to accurately separate fine details such as hair from a background.
To overcome these limitations and improve the quality of footage created using compositing, special effects engineer Petro Vlahos developed a new compositing technique in the s. By using a revolutionary process involving 12 separate compositing elements, Vlahos' technique could remove blue or yellow backgrounds from scenes while preserving fine details such as hair. While computers have now replaced optical printers, the chroma key technique is still based on the same process Vlahos invented more than 60 years ago.
Nowadays, special effects artists and TV producers rely on chroma key to shoot countless shows and movies, from morning talk shows where weather forecasters deliver their predictions in front of a virtual map to fantasy shows such as Game of Thrones where realistic dragons interact seamlessly with actors. The resulting video output is the weatherperson superposed in front of the weather map. Blue screens work almost as well. Because green and blue are both well away from orange-red on the hue circle, both are suitable for chroma-keying people.
If Kermit needed to be keyed on top of a background a blue screen would be essential, whereas Superman needs a green screen. Film-based compositing methods preferred blue screens, due to the availability of blue-sensitive films. Green screen works slightly better for video as there are more green-sensitive pixels in common camera designs than red or blue. And blue coloured clothes are harder to avoid than green ones. All sorts of other colours have been used, including magenta, and even white screens lit with bright yellow sodium lamps used to superpose Mary Poppins over London.
Portsmouth Climate Festival — Portsmouth, Portsmouth. Edition: Available editions United Kingdom.
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