Friday, January 1, 2021

Using a Green Screen for Streaming

One of the most popular accessories for Twitch streamers is the green screen. This is a large, flat, single-color surface which allows the background to be removed from your shot. The effect is similar to that of a TV weatherman, allowing you to cut yourself from the frame in your stream software and replace the background with any image or video of your choosing. Most of you are probably familiar with what a green screen is, but it's common to see streamers who don't entirely understand how best to take advantage of this tool. In this entry, we will go over how to properly set up a green screen to prevent many of its largest problems. 

I will however, begin this entry the way I begin every entry of this sort. Pay special attention if you've never been with The Twitch Playbook before and you skipped to this entry first: EXPERIENCE is always more valuable than a perfect looking stream. If you haven't done at least a dozen combined hours of broadcasts on your channel already, put this entry down and start streaming right now. You can come back to add or optimize your green screen later. If you still don't think you're ready to stream, see the entry Start Your Twitch Channel with No Money. This entry is meant for those who are already consistent at streaming and want to optimize their shows- if you haven't streamed yet, employing these tweaks will be just another way to procrastinate. There's no excuse not to start your journey today.


You could look like you're on an alien planet!

Green screens take advantage of a concept in your stream software called 'keying,' which means the program will turn all instances of a single color invisible, wherever it sees them in your camera shot. There's nothing more fancy about it than that. There's no special equipment required if you don't own an official green screen either- the effect can actually be accomplished with anything. You can clamp a green blanket to two lamp stands so it hangs behind you, tape green construction paper to a big piece of standing cardboard, or even sit in front of a green wall. The removed color doesn't even have to be green- you can remove whatever color you choose. The reason green is the industry standard in TV and film is because out of all colors on the spectrum, bright green is the one found least often in any human skin tone. This means that, unless you want your face to become invisible, green will be your best bet. But you could also get some interesting results should you choose to experiment. I've seen some really cool psychedelic-looking visuals from streamers who intentionally key out other colors on their shows. 

When using a green screen, many streamers fundamentally misunderstand what's important. Most assume that putting up the green screen itself is the first and last step, but then wonder why there are glitches or inconsistencies in how their stream removes the green background. Merely putting up the green screen will only work in a few very specific situations. In reality, that's only the beginning of the process. 


The real concern with green screens is not the equipment itself, but the way you hang and light it. Anyone who has worked on a film or commercial set using green screens knows this already, but the power of a green screen comes from your ability to make it look like one single unified color in the lens of your camera. This sounds simple, because the green screen itself is already one color, but the process is actually anything but. As I've mentioned in the entry Focusing a Streaming Webcam, cameras don't see the world in the same way we do. And green screens make that very clear.

If you own a green screen, have there ever been times when sections of yours start peeking through the key, and you see green splotches from your background appearing in front of your game? Or how about times when chunks of your own body start blinking out of the shot? These are common problems which occur when there is a bad key. This usually originates from the way your green screen has been set up in the first place. As I mentioned earlier, the software looks only for one exact color when keying out your green screen. And even through the green screen itself is innately one color, any darker or lighter areas within that green will make the software no longer recognize it as the specific shade of green that gets keyed out. 

A bad key can make it look like parts of your
body are disappearing.

Now, there are custom settings governing the range of green shades the software looks for, which I won't cover here, but the most fundamental thing to keep in mind is that you want to eliminate shadows in the green screen itself. On a film set, this usually means stretching the green screen tight so there are no folds, and pointing diffused lights directly at the green screen to make sure it's evenly lit. If the lighting which points at your face causes you to cast a shadow backwards onto the green screen, you would want to either move the green screen further back, or move the lights higher so those shadows fall further downwards and avoid hitting the green screen. It's also possible to go too far in the opposite direction, creating a 'hot spot' on your green screen from too much light. Keep your lights diffused when they point at the green screen by either moving them physically further away, or getting some diffusion paper for the lights to make their beams less harsh. In the entry How to Make Your Camera Look Better, I covered several of the most important aspects of properly lighting a stream, even if you own no professional lights. Understanding those concepts will come in very handy when trying to set up a green screen properly.


Even the best green screen money can buy is nothing more than an expensive piece of green cloth. Everything comes down to how you use it. Bad lighting will make the best quality green screen look terrible just as easily as good lighting can make a cheap green screen look great. If you don't have a green screen already and want to use one, I suggest trying to make one yourself. It's possible to buy the parts required for less than $10, assuming you don't have anything usable at home already. All you need is something green to fill the background of your camera shot behind you. What that thing is, is up to you. Your stream software is pretty smart, and it'll give you a lot of room for error when setting up your green screen, but it's not perfect. When you take the time to properly set things up, it will remove a lot of headache. A well-implemented green screen can add a very professional look to your shows. So put that extra time in, to make your streams look a whole lot better!  

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