HOW DOES GREEN SCREEN WORK?

Videomaker by

How do you move characters around in a world that lives only in your imagination? By following this easy step-by-step guide to going green.

Through the magic of video effects and technology, you can superimpose your subjects onto virtual backgrounds, place them over animated digital backdrops or transport them to a desert oasis. You can shrink down a full-grown man so he can stand on a tabletop, use visual effects to make him fly through the sky like a superhero or simply simulate your own TV weather report. But to do it right, you’re going to need a lot of green. No, we’re not talking about money. The green we mean comes in the form of a green screen. The secret to pulling your subject out of the real world and placing him or her into a digital domain is chromakey, and that means going green. In this article we’ll cover all the essentials you need to know to pull off keen, clean keys and composite digital backdrops and virtual backgrounds into your edits.

What is Keying?
Keying is the process of isolating a single color or brightness value in an electronic image and using software to make that value transparent, allowing another image to show through the affected areas. Luminance keying, or lumakeying, is the process of keying out a brightness value or range, like black or white. Luminance keys are often used for applying mattes. Color keying, or chromakeying, identifies a specific color to remove.

Why Green?
Many people use the terms chromakeying and greenscreening interchangeably, but the principle that powers chrominance keying is not limited to the green parts of the spectrum. In the visual effects world of Hollywood, blue screens are far more common than green. In fact, you can key out any color; red, yellow, purple or pink, blue and yes, green. So why is that odd and ugly shade of green the hue of choice for television and video? The biggest factor is contrast. In order to isolate one area from the rest, the background color must be distinctly different. read more...