Composite Green Screen Footage with Motion 5's Keyer
Using the keyer to composite green screen footage
There's really nothing more exciting to new designers than the first time you pull a key. Being able to make a background transparent can really help you create all those fun effects, with people floating over colorful backgrounds, riding roller coasters, flying like Superman, you get the idea. Now if you're a long-time designer, pulling a key may not have been something you would've look forward to in previous versions of Motion, but I have to say in Motion 5 the Keyer is nothing short of amazing. Now before we get started with this project, let's actually see what we're dealing with. Press F5 to open your Project panel and I'm just going to close my File Browser by pressing Command+1 here, and you'll notice I have this GS-- green screen--Dancing QuickTime, and then I have these two backgrounds that are just generators.
They are different color solids, which you'll understand why I'm using these in a little bit once I pull my first key. Now with the green screen Dancing filter selected, let's go down in our toolbar and click on Filters. Notice there is a whole section for Keying, and now all we have to do is go to Keyer. And it's pretty amazing: the very first time you apply a key with Keyer, it almost nails the key just about every time. It's pretty insane. To look at some of the options with the Keyer, let's open the Inspector.
Press Command+3 on your keyboard, and you'll notice the Keyer has a couple of different sections here. Now by default, the Keyer will automatically pull a key based on whatever color it sees as most dominant. So notice there are no settings for green or blue key. It just looks at the image and then pulls a key. Now I have two different backgrounds that I like to look at keys with, and that's just because I found these two colors are pretty good in terms of contrast when you're trying to see how clean a key is.
Now if you're unfamiliar with exactly what I mean by clean key, let's just preview things here in a second, and take a look at things. I'm going to press the spacebar to begin playback, and you will notice okay, she's dancing around the screen and I'm still not seeing any green. If you Turn off the Gray layer, now you notice we can see red and if I stop playback here, you'll notice a couple of things. First thing, notice it actually keyed up the center of her shirt. Now we're going to deal with that actually in the next movie using something called a holdout matte.
Now for this movie, we'll just leave that alone and analyze something a little harder to deal with, and that's things like hair. Usually when you shoot something on green screen somebody has hair flying around and that sort of thing, you really need to make sure that the background-- here if we turn the Keyer off--that the background is nice and solid like this. The people I've shots this did an excellent job lighting the scene, because you notice, there's no shadows. It's evenly lit. It's a really nice situation. Now, when you first apply the Keyer, it does a great job in Automatic mode.
Now the way that that works is with this Strength parameter. See, if I drag the Strength parameter all the way to the left, notice the key is gone. This is how you can actually pull your own individual custom key, and the way we do that is using the Refine Key section here. So click on Sample Color and just draw a box over here on the right-hand side of the interface. Now notice as I draw this box, on this red background I'm seeing all this white that's going around here.
This is caused by the values of this green being slightly different than the values that I chose to key. Now if want to key let's say this and add that to this current key, all you have to do is hold down Shift and drag another selection area and then that refines the key. Now notice the edges of her hair still have this kind of white edge to it, so we can actually use the Edges selection just by clicking on Edges. And the way this works, you want to just click and drag over the area that is semitransparent, so the area that you want to be able to see through.
Now I'm just clicking and dragging and once I let go of my mouse notice I have the Adjust Items tool automatically selected, so I can click on the slider and adjust just how strong the transition is through this area and if I drag it too far to the left, notice it starts actually keying her out as well. So I just wanted to key out a little bit of the edges, but not too, too much. Now if you find that the exposure and your image changes slightly as you move down the timeline, you can add more keys just by making sure the Keyer is selected, click on Sample Color, and then click and drag.
See, when I do this, now notice I have jumped to sample, see I've two different samples because I sampled on one frame here at 03:15 and I sampled on another frame here at 05:08. So this is how you can refine your matte as you continue adjusting things. Now since we've keyed out the background, you'll find as you work you want to actually be able to view the mask that's being created. So, if we click on this View option here in the center, you'll see this is the map that's been created, and then if you click on the right button, this will always show you your original footage.
Now there are few more settings right here in the top section of the Keyer that I want to get through, and let's check them out. This first option here for Fill Holes, it'll be easier to see if you click on the Matte option. When you click Fill Holes, see what it's doing? It's actually filling in the areas that it sees as a hole and as it's filling those holes, it's making the matte more dense and it's just trying to fix any areas where it's supposed to actually be keyed out. Now if we go back to our composite image, notice as I crank this up it's generating a harder edge for the mask here, it's filling in some of the areas of her hair that I don't want filled in, and now it's not showing me the green that used to be there, but it still giving me these light pixels, so we'll leave Fill Holes deselected for now.
Now the Edge Distance is kind of interesting, because this works in conjunction with Fill Holes. See, as I drag the Fill Holes parameter here, the Edge Distance allows me to specify exactly how far from the edge I want this Fill Holes parameter to fill in. Now the last thing I want to cover here in this video is Spill Level. See, if I click on Spill Level and drag, notice I'm starting to see the green come back into our dancer. Notice the background is still keyed out.
Whenever you shoot anybody on green screen, typically what ends up happening, there will be a little bit of a green tint that bleeds into whatever it is. Now with our dancer here, it was just the edge of her skin tone and since I have a rather rough key applied with the manual key, notice it's given me kind of a strange effect. But if you ever pull a key and you notice somebody's skin tone has done this and it's turned kind of magenta, you might want to bring this Spill Level down a little bit and it should bring the natural tone back in.
Now there are many more options within the Keyer, but we will jump to those in the next video.
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