Why is a blue screen used sometimes in movies and other times it is a green screen? Am I incorrect or is the green screen used more today than the blue screen?
Since the purpose of the green/blue screen is to give the editor a solid color so that a background can be added in later, they change the color depending on the surroundings. Obviously, if the actor is wearing a blue suit, you would use a green screen. If there were a lot of trees in the foreground, you would use a blue screen.
The entire idea is to have the screen a color that exists nowhere else in the shot, so when you tell a computer to remove all instances of that color, you don’t zot something that you didn’t want to.
As long as the screen is a solid color that is not used in the actor’s costumes, it doesn’t really matter what color is used. All they need is a solid color background that they can remove easily. Using computers, they just remove all of the green/blue from the shot, then layer that image on top of where they want to superimpose the actor’s image. I’ve seen some local commercials where the actor’s costume contained the same color as the background, and you could see the background image through several holes in them. It looked funny, but wouldn’t fly in movies.
I would hazard a guess that it depends on what is going to be appearing in front of it.
For example, if the foreground includes a lot of blue, the green screen is used. If the foreground is green, a blue screen is used.
Also, a color like blue is so…well, blue. I would think that there is enough blue clothing around that for the older systems, it would be difficult to pick what is to be shown in the foreground and what is to be filled in from the background. The newer system can probably find not only the green, but a particular shade of green.
That’s just a guess, anyway.