Join Chad Perkins for an in-depth discussion in this video Removing a green screen background, part of Premiere Pro CS5 Essential Training.
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Oftentimes if you want to put people in a different environment, let's say on a virtual set like this, we'll film them in front of a green screen, and then in Premiere as we talked about in the last movie we'll remove that green screen. Why is it green you asked? Because green's opposite is magenta, which is very strongly found in flesh tones. So, green is kind of like the opposite and so the thought is that we would remove the green and keep in what is there in our subject. Also, green tends to be a color that video cameras can handle pretty good.
So, the process of removing green screen is referred to as keying. If we go to the Effects panel, open up Video Effects and scroll down, we'll actually see that there is a category called keying. If we open this up, there is a series of effects to help you key and you can just key out the green screen, but you can also key out blue, or red, or white, or black or whatever, there are several effects to help out here. And there is a new one here in Premiere Pro CS5 called Ultra Key and that's really what we're going to be focusing on here. That is an amazing effect, absolutely amazing.
But what I want to show you here is the old way to key just so you don't forget to use Ultra. We used to have to use the Color Key effect. If I apply the Color Key effect, open up Color Key and select the Key Color. Let's say I'm going to select a green color here. So, once we click the green, we have to increase the Color Tolerance value and then we get this really chunky ugly outline. Look it, how terrible that looks. If I'm going to take this drop-down here to 100% so we could see a little bit better.
Look how atrocious that is. That's what we have to deal with before Premiere Pro CS5. So, I'm going to select the Color Key effect, delete that, good riddance, scroll-down now and apply the Ultra Key effect to this Podcast Pt.1_3 clip. Now we can go back to Ultra Key, open that up and the same thing we're looking for the Key Color. It's asking us what color I want this to remove and notice it could be any color if we want to. So, I'm going to click the eyedropper again and what we want to do is select an average color. Now, this is a pretty perfect green screen, I got to be honest with you.
Usually, if you're working freelance on a job, usually whoever is doing the green screening it doesn't really know what they are doing as much and you don't get a green screen that's this professional. So, you want to try to do when you have a green screen with varied tones is get when this kind of representative of all tones, kind of average. Thankfully again, we don't really have too much difference in tones so pretty much in anywhere in this green area you can click. Now, if we zoom out to Fit here, I will select Fit so we could see everything, pretty darn good key, looks like the backgrounds but instantly dissolved and our guy here looks like he belongs on those background now, pretty impressive.
However, almost never, do you ever, ever, ever want to just accept the default settings of the key, no matter how good it looks initially there are always problems beneath the surface. So, what we want to do is open up our Effects here and under Output next to Ultra Key or underneath the Ultra Key, change Output from Composite, which is kind of like the final view, to Alpha Channel. Now, Alpha Channel view is just a working view, a temporary working view for your own benefit so you could see what the keyer is really doing, and white are the pixels that are going to be completely opaque which is our subject which is good, and black is what's going to be completely transparent, and some of our background pixels are completely black which is good.
But when you see gray pixels like this, it's indicating that these pixels are going to be partially transparent. And actually if I take this view back to Composite, you'll see little flakes of the original background here. It's not too powerful but that would definitely be a problem. So, I'm going to take this back to Alpha Channel and we're going to open up Matte Generation, and these settings in Matte Generation will allow us to clean the stuff up. Mainly, we're going to go down to Shadow. Transparency refers to the transparency of the subject.
Beware that this is not Opacity. Opacity and Transparency are exactly the opposite. So, 100% Opacity would mean that something is completely there, but 100% Transparency -- if we took this up to 100 %, would mean that it'll be completely gone. So, I'm going to click in this, leave this at the default 50 for now and again go down to Shadow. With the Shadow value we can adjust the blackness of the background. So, I'm going to take Shadow down pretty much all the way, looks like to about a value of 15. Generally, you want to go pretty easy on these controls because if you go to an extreme amount this is going to start messing up your key in other places.
And already just taking our shadow down all the way we start getting holes in our original subject that we have to go back and fix which we'll do momentarily. We could adjust the Highlight as well which we need to clean up this background here. We also might need to adjust the Tolerance and so we play with these settings until we get the right values to get rid of that green screen. We're also wanting to adjust Pedestal here. Increasing the Pedestal just a wee bit, just as much as you need. That looks like I am modest here with the value of 6 here and that gets rid of that green screen.
Now, I need to fix these little dark spots on my subjects here, because again the dark areas are holes and we definitely don't want holes. So, I want to reduce the transparency of my subject and I'm going to do that by taking the Transparency value down. You see if I do it too much then we get that junk back, so we don't want that. So, I'm going to increase this until I get the holes in my key and then back off a little bit and that's looking pretty good right there. Usually, Keying is a back-and-forth process, so we'll adjust Transparency and then we might go back and adjust Pedestal or Shadow and then we go back and adjust Transparency some more, go back and adjust Pedestal some more or whatever.
We keep going back-and-forth until we get a pretty much white key and black key, or in other words white area and black area. And by the way it is okay to have those gray pixels along the edges of your subject. Now that our keys are pretty good, let's go back to Output and change this from Alpha Channel to Composite, and we'll see now that we have a pretty good key. I want to take the zoom ratio in the program monitor to 100% so we can get in a little bit closer and look at our edges here. We have a little bit of a faint greenness along the edges that's referred to as Spill.
Also some of the green light gets on our subject, or maybe just some of the background gets on these partially transparent pixels here and it's just gives us like a little green halo that -- if we get rid of that, it's going to make it so that the composite is a little bit more believable. So, what I'm going to do is I'm going to close up Matte Generation. We have Matte Cleanup, which we don't really need to worry about, but Choke allows you to kind of scale back the edges of the key. You got to be careful with this because a lot of people, they are amateurs, they would go in and they will start keying something and they will see these problem areas around the edges and they will say okay I will just increase some Choke and what that does, it actually softens the edges and it makes it so that it's not as realistic and believable because as we're increasing the Choke we're shaving off the edges.
So, that's not typically what we want to do. So, again I want to take that down. If you ever do need to use Choke use it very sparingly. We could also soften or feather the edges just a little bit. And sometimes it's good to have just a little bit of feathering along the edges so that it looks like the subject is kind of blending in with the background a little bit more. If we want to we can play with the contrast of the edges, increase that, if we felt so inclined we can also use the Mid Point to adjust that as well. I'm going to close up Matte Cleanup. I want to go to Spill Suppression and as I mentioned before when you have green along the edges of your subject that's referred to as spill, and Spill Suppression is the process by which we get rid of that green.
So we might take down Desaturate just a little bit and I say that looks like what we need to do there. If we take it down all the way or increase it all the way, it's going to make up completely black-and-white subject. So, again you might need to play with this setting, kind of go back-and-forth a little bit until you get something that works for you. So all in all, if we close up Ultra Key here you can see that we have a pretty decent key. One of the processes that I did before I started the movie is I added this Four-Point Garbage Matte. Oftentimes you'll have extra junk in the shot, maybe again like a boom mic or a camera or whatever and you'd want to use a Garbage Matte effect to clean that up so that your mask goes only around the subject as close as possible, and that will make the keyer's job easier as well.
Because a lot of times when you go farther away from the subject whoever was filming this just didn't bother to get the entire shot perfectly green all the way around. So, it's going to be harder for Ultra Key to do its job if it has to process the darker greens over here and the brighter greens closer to the subject. But the Ultra Key effect is just a really great edition perhaps the best edition to the Premiere Pro CS5 set of new tools to play with. With this Ultra Key you can put somebody flying in front of a green screen in outer space or whatever you choose to do.
If you want to do something a little bit more standard and professional like a Podcast here you can do that as well. There is really no end to what you can do creatively by using a green screen.
- Adding footage to the Timeline
- Creating dynamically linked content
- Making overlay and insert edits
- Moving edit points
- Playing a clip backwards
- Understanding pixel aspect ratio and frame rate
- Applying motion effects
- Cutting video to music
- Compositing with green screen and blend modes
- Correcting color
- Creating titles and lower thirds
- Exporting sequences