Green Screen

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Green Screen Technology

George's Digital Technology is your solution to streaming live video to your social media pages, or other streaming providers you may have. 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 green screening 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. Bright green beats blue partially because it is not a color commonly worn by talent. Any clothing that matches the background too closely will also key out, punching a hole in your subject's body, or making him invisible altogether. We narrowly escaped a chromakey crisis a few years ago when I was working at a Northern California TV station. One St. Patrick's Day our wacky weatherman showed up to work dressed head-to-toe in a bright green leprechaun suit. Fortunately, we quickly pointed out the flaw in his logic and he was able to find a change of clothes before it was time to go live.

What do I Need?

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.

The most obvious need is for the background itself. Fortunately, there are many options, and many of them are inexpensive. In short, anything that's bright green will work, and anything that works is valid. I have produced professional green screen scenes using giant dedicated cyclone sets, large professional fabric chromakey backdrops, sheets of material purchased by the yard from a fabric store, smooth walls or pieces of paneling painted with a gallon of dinosaur-green paint from the kids section of the hardware store, even sheets of green poster board taped together. (NOTE: Be sure to avoid textured walls if you're painting it green. Texture causes shadows.) The only requirements are that your background be large enough to fill your screen, smooth enough to take light evenly without showing wrinkles or casting shadows, and bright enough to contrast well with your subject. If you intend to chromakey a sock puppet your backdrop may be relatively small. If you need to chromakey a full-body shot of an adult actor, you will need a much larger background. If you are experimenting with chromakeying for the first time, you can test the process on a small scale before you build a big set. You can quickly create a functional miniature table-top set with an action figure and a sheet of posterboard. It doesn't take much more effort, however, to stretch a sheet of green fabric between two step ladders or to paint a small section of wall.

Many people use the terms chromakeying and green screening interchangeably, but the principle that powers chrominance keying is not limited to the green parts of the spectrum.

Even a professional-quality cyc wall won't key well without proper lighting. If there is a secret technique to getting good keys, it is in lighting the wall. The goal is to light the set as evenly as possible using soft light. Any variation in lighting will read as gradient coloring and will complicate your key in post. Achieving even lighting can be more difficult than you might think. Hard light sources cast narrow and focused beams that create circular hot spots in their center, then fall off rapidly leaving outer portions gradually darker. It helps to move small lights farther away so they cast broader, soft light beams. If you have access to soft boxes, they are excellent options for casting evenly spread light. I have had great success lighting green screens with long tubular fluorescent fixtures along the top and sides of the backdrop. You can get a six-foot garage-style fixture from your local home hardware store for less than lunch. These fixtures cast a soft light that is quite appealing for your green screen. You don't want to light your talent with a flo-fixture, but when you are lighting a green set the color temperature of the instrument is not as important as lighting your background evenly.

Another important, but often overlooked, essential is lighting your subject independently of your set. This is important for two "key" reasons: shadows and reflections. Part of keeping your wall evenly lit is keeping your subject's shadow from falling across it. To do this you need to position the talent at a distance of at least a few feet from the screen, and light him separately using three point lighting. We offer green screen set-up services, call today!

We will set-up your Green Screen and Lighting if you use a Live Video Production Software, we offer training, how to bring inputs into your software, set-up presets, titles, lower thirds, virtual sets, images, photos, overlays, audio, videos, PowerPoint's, NDI, desktop capture, cameras, and more. We offer Laptop Key Programming, we will program your laptop keys to work with your software, your iPad, or Android Tablet.    

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