Most of the times, especially on science fiction movies, we see actors flying or riding dinosaurs backs. We also see them defying the laws of gravity, or standing in a place that we cannot imagine that it exists in the real world.
In addition, we also encounter dreamy scenes, magical places, and out of the world nature views. Sometimes, actors are standing in a city we have seen before, and suddenly something change; the actor himself or herself transform into a bat or whatever, and a place that we have never seen appears. Have you ever wondered how producers do that? Or how can an actress become a cat or anything else? This is what green screens are for!
Which also means green screen, consists of backdrops of brightly colored fabric or paint, which is usually vivid green colored, that help induce all of this high-tech fakery. In fact, Chroma keying allows producers to separate the actors or people from the green background, and replace the background with pretty anything they want, such as sceneries, dragons, animated backgrounds, etc…
The green screen is used by taking a previously recorded video, and isolates and removes a single color in a narrowly defined region of the spectrum. Usually, the color of the screen is bright green or blue due to the fact that the two colors are different from human skin tones and are not usually present in the actors’ outfit colors. Additionally, Chroma keying for live feeds requires hardware that can recognize and manipulate multiple video channels — layers defined by color — while recorded material can be changed in post-production with video- or photo-editing software.
In fact, this is the most used process in the post production of science fiction movies. We all know now how Harry Potter movies’ effects are made!