What is green screen? || How to use green screen in VFX effect

The secret to pulling your subjects out of the real world and placing them into a digital domain is chromakey, and that means going green with green screen.



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.
Chromakey allows you to take your subjects out of the real world and placing him or her into a completely new world. 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 chroma 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.

Green screen requirements

You can erect a simple chromakey setup almost anywhere with just a few basic tools. In order to shoot footage that will key cleanly, you will need a green background, a source of bright, even lighting, and a tripod to lock your camcorder in place. We will cover each of these elements in detail.
Lock your tripod down
Unless you are planning to use motion tracking markers and a complicated visual effects compositing software to motion track your subject into a virtual 3D environment so that the movement of the camera perfectly matches that of the digital background shot, even the smallest camera motion is unacceptable. This is a case where it’s got to be all or nothing. Either commit to motion tracking or use a good tripod, and take your hand off when you roll to prevent any vibration.

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