Learn about using Chroma key Studio to remove greenscreen.
- [Instructor] We're moving on to another important aspect of visual effects compositing, and that is chroma key, or greenscreen removal. Here's an example greenscreen shot to work on. This actually features one of our producers riding his unicycle on a greenscreen set. Let's play it back. There we go. There are some nice things about this, including the fact that he's completely surrounded by green. Now, it's not perfect, and there are some issues we have to work our way through, but those won't be too hard.
This scene is saved out as 4_1 in the chapter four folder. Okay, so let's talk about how to chroma key this. And there are a set of Boris chroma key tools. I'll select the layer, go up to Effect, and these effects are in the Key & Blend menu. Now, some of these effects deal with certain steps of the whole chroma key process. For example, the matte choker or matte cleanup. There's also the chroma key effect. Now, if you want to combine multiple effects together into one workflow, there's also the chroma key studio.
This takes a number of these individual effects and combines them in one place. This makes the workflow for greenscreen removal much more efficient, so let's apply that chroma key studio. You see that this effect has a number of different components, including masking, the actual chroma key removal, matte cleanup, matte choker, color correction, light wrap. Normally these would be separate effects, but here they're all in one place. I'm going to start by actually using one of the masking tools. I'm going to switch the outside mask shape from Off to Rectangle and essentially get myself a garbage mask to get rid of most of the greenscreen.
I really should only work on the part close to the actor to make him more efficient. You can grab the top left and bottom right handles and drag those to limit that area. I want to make sure I'm not cutting them off, but I do want to minimize the amount of green I'm working with. All right, that's pretty good. Now, the chroma key component's already on by default, and that's what we use to remove the green. Let's give that a try. I'll expand the chroma key rollout, and it's not doing much yet, but if I pick the key color it'll start to work.
I'll use the eyedropper. Select the green someplace in the center, where it's nice and evenly lit, and there it goes. Starts to work. It's not perfect, but it's a pretty good start. Now, whenever I chroma key or remove greenscreen, I like to put a new background in to test that removal. Even if it's only temporary. So, for example, I can add a solid as a lower layer. So Layer, New, Solid. I'll make it the comp size, and some color that's very different from the foreground, for example, this bright red.
And I'll place that below. Now I can see how well it's working. For example, there are a few issues here where there's red showing through some of these holes. I'll return to the effect. All right, so what do we do next? I want to get the matte looking a little bit better. The first place to go is the Density, Balance, and Lightness sliders. Density controls the density of the opaque matte. Lightness controls the brightness of that matte, and Balance tries to balance between the density and the lightness. So what we can do is experiment with these sliders and see if the matte gets better.
Now, look at the matte, there's a built-in view option right here. View Options, I can switch from Final Composite to Chroma Key Matte, and there's the alpha matte. Let's concentrate on his body first, let's try to get rid of some of these gray holes. If I raise the density, that helps improve it a little bit. If I lower it, it gets worse. So let's go up to 200 on density. Lightness, if I go down it helps a little bit, if I go up it's worse. Be careful not to get noise into the background.
So I might just leave Lightness at the default 40. Let's try Balance. Going up helps, some of those holes go away. It also expands the edge of the matte. So maybe a little bit higher, like 165. Now, that hasn't solved everything. For example, adjusting those sliders has added some noise into the ground, like where the shadow is, and it hasn't really helped the tire. The tire was suffering to start with, I can't see the spokes, and there's some gray in there.
We'll probably have to deal with that in a separate step, which we'll get to later on. Now, there are a few other sliders we can use to try to improve the matte at this point. There are also the red, green, and blue weight sliders, and this helps balance the tool towards or away from a particular color. By just experimenting with these, you'll see different results, like higher red, lower red. Some differences. Same with the green. Lower green, definitely a lot worse. It ignores the greenscreen, essentially. Higher green starts to erode a lot.
And then blue. Lower on blue actually helps the noise on the ground. So I just have to balance these out. Let's say 80 on red, 60 on green, and 65 on blue. Actually, that's allowed some of my spokes to reappear, but now I have more noise on the ground. Again, I think we'll deal with that noise in a separate step through some of the other built-in components.
And we can use, say, matte cleanup and our matte choker to help deal with this down here. All right, one last thing to work on at this early stage, and that's the spill. Let me go back to my final composite. Whenever you shoot something against greenscreen, like this actor, there's going to be green reflected light that gets on his skin, on his hair, on his shirt, and so on. Very difficult to avoid. Now, the tool, or the effect, tries to remove that, and how it does that is based on the spill sliders.
For example, spill ratio. If I raise the spill ratio, it leaves more of the green in. If I reduce the spill ratio, it's more aggressive towards its removal, to the point where there's pretty much no green left and you have more blue and red so he looks purple. So I'm going to adjust this. I might leave a little bit more green in so it's not too eroded. And then I can use a different component to try to balance that so it's less green. I can go back to the color correction component later on.
But there's going to be some green there, so you might want to take a look at the spill adjustments. Okay, that's a good place to stop for now. We're going to move on to these other components in later videos and try to improve this greenscreen removal.
VFX expert Lee Lanier begins by exploring shared Boris Continuum controls, and then shows how to apply stylistic effects. He explains how to work with the PixelChooser and Boris Lights, and discusses how to color grade and warp footage. He also takes you through using the Boris Chroma Key Studio and working with Mocha Pro for motion tracking, as well as how to add particles and work with 3D text.
- Overview of Boris Continuum
- After Effects preferences
- Applying stylistic effects
- Relighting with Boris Lights
- Adjusting colors
- Changing the time of day
- Warping footage
- Keying green screen
- Motion tracking
- Adding particles
- Working with 3D text