Have you ever seen a movie in which a superhero flies through the sky? You can see all the skyscrapers whizzing by in the background, and it looks so cool. Have you ever WONDERed how movie makers film such shots?
Well, we're here to tell you the secret. And the secret is: there are really superheroes and you just have to catch them in action! OK, not really, but the special effects professionals who work on movies are like superheroes, because they have invented some incredible ways to create special effects shots that will knock your socks off!
You don't have to watch a superhero movie to see special effects in action, though. All you need to do is turn on the news and watch the local weather forecast. Have you ever noticed how the meteorologist sometimes stands in front of a map with moving graphics? Those scenes are created in much the same way that those cool movie special effects are created.
The special effects created during weather forecasts and many, many television shows and movies utilize a special tool called a green screen. Why is it called a green screen? Mainly because it consists of a large screen that is green!
The green screen is an integral part of the special effects process known formally as chromakey. Chromakey allows television producers and movie makers to use advanced technology to superimpose their subjects onto an unlimited number of different virtual backgrounds.
Chromakeying, sometimes known as color keying, is the process of singling out a particular color in an electronic image and then using computer software to make that color transparent. This allows another image, which can be just about anything you can imagine, to show through.
For example, when a meteorologist stands in front of a green screen, television producers use the chromakey special effects technique to isolate the particular shade of green used on the green screen. Computers with special advanced editing software then make that shade of green effectively disappear, allowing another image — such as the animated weather map — to show through instead!
When a superhero movie is filmed, the actor portraying the superhero might be filmed in front of a green screen lying on his stomach with a huge fan blowing his hair and cape back behind him. Chromakeying can then replace that green background with a moving image of the night skyline behind the actor, making it appear as if he is flying through the sky.
Some of you may be WONDERing if screens have to be green for chromakeying to work. The answer is no! Any color can be isolated and removed via chromakeying. In fact, many movie makers use blue screens. You could even use chromakey to remove red, purple, orange, yellow, or pink!
So why is green such a popular color for screens? The answer to that question lies in the concept of contrast. The screen being used must be different from — contrast with — the actors being filmed. The shade of bright green often used for green screens happens to be a color that very few actors are likely to wear, so it's easier to isolate and make transparent.
If an actor happened to appear in similar green clothing against a green screen, chromakeying would make any such clothing disappear, too, leaving you with just a talking head! Of course, that might make a cool special effect of its own!