Original subtitles

In this clip we're going to take a look at despill with the keylight tool.

So often when combining multiple keys and mattes,

the image is despilled separately from the final alpha.

Chroma keys are often built to have two major functions.

One, to pull a key, and two, to despill the image.

So let's take a look at our script in more detail.

So here is our image sequence, and we're going to add a keylight tool,

and before we begin we're going to add an alpha to our image.

So if I double-click on my image and I scroll down in the

Properties bin we can turn on Auto Alpha.

Let's take a look at our alpha.

Here it's made the entire canvas 100% white in the alpha.

Or we can do a second option, which we add a shuffle node.

There's a shuffle node,

I'm just going to turn off the Auto Alpha and shuffle

100% white into the alpha instead.

So either one of those is acceptable,

but it's really just your personal preference.

I find that a visual cue often helps, so if that works for you,

feel free to add a shuffle node.

So hook up the source input,

and I'm going to connect the InM over here just so that

we can see it a little bit easier.

Now if you need a refresher with all the different inputs for the keylight tool,

I do suggest that you refer back to a module earlier in this

course named Combining Multiple Mattes.

In that particular module you'll find a clip named

Combining Core and Fringe Mattes with Keylight.

And there, we looked at the keylight input in more depth.

So now that we have the InM selected,

we're going to hook it up to the shuffle node or to the

original image if you had an alpha there.

InM is the inside mass or core matte,

and we're going to tell the keylight tool to make

the entire canvas the core matte.

So scroll down to the bottom of your Properties bin for the keylight tool,

and then, under Crops, there's the InM component and OutM component.

Under InM, our core matte, we're going to say alpha,

and now it's going to make sure that the entire

canvas is our core matte and that we, essentially,

can't pull a key.

So let's take a look at our image and go to full color,

and we're going to just say, please, just get rid of 100% of that green.

It's despilled the image, but our alpha remains untouched and 100% white,

which means that we have separated the despill from

the keying process in this tool.

So now let's take a look at a different way to do the same thing.

So this is personal preference.

So again, here's the keylight tool, but I don't have to select the InM,

or hook it up.

We can select the keylight tool and scroll down to the bottom,

and instead, this time, go to Inside Mask.

So by default, the source alpha will be set to Ignore,

so it's ignoring that source alpha just so that we can pull a key,

essentially, so pull a key and to do the despill.

So here's a keylight, we want to say, please take a look at that alpha,

and we want to not pull a key, but just despill.

Do that again, full alpha, and there we go.

So it is doing the same thing again, it is doing the despill,

but not changing my alpha, which is exactly what we want.

So now that we know how to set up the keylight tool

so that it doesn't pull a key,

let's take a look at the couple of different options that

we have in order to despill the image.

So here we go, so here is our image over here,

and we're going to take a look at the keylight tool.

Again, it's hooked up to the InM.

And I can do one of two things, I can either,

A, despill 100% of the green, so here it is,

100% of the green.

Just say one.

The problem with this is sometimes it's quite aggressive,

so be careful that it's not going to push those colors too far,

especially because there was never 100% green in our backing region.

However, there is a benefit to doing this,

and that is that our backing region has actually matched

the color of our character's hair.

So a lot of times what'll happen is that the color of the backing

region will not match the edges of our character,

or object, which will leave a halo once it's pre-multiplied.

So for her hair this is actually working really fantastic.

However, once it's pre-multiplied, we may get a brown halo next to her jacket,

so we will take a look at that in more depth in future

clips in this particular module.

So let's take a look at the second option.

So the second option is to actually select the green inside of this image.

So let's add a new keylight tool, there's our keylight.

Let's hook it up to the source, hook it up to the InM if you wish.

Down here, alpha, so it's not going to pull the key.

We're going to say, select the backing region color, so there we go.

Let's try that one more time, there we go.

So it's neutral gray.

Take a look at these values,

it is almost identical across the board with the RGB colors.

So the problem with this is now not only does it not match her hair edges,

but it also does not match any other part of this foreground character either.

So not only will it pull a edge, or a gray edge around her hair,

but also for the rest of her body.

Let's take a look at the two different images.

So here is it before, where it matches her hair,

and here is where it is where it's gray on the outside and,

again, quite the difference, but minimal changes in the core of my image,

which is probably a good thing, just for my edges over here,

where it will be semitransparent.

Now this is often an issue,

edge work is one thing that we really want to take a look at

when we're finally in our integration.

We're going to take a look at different ways to change this or to

modify it in future clips in this particular module.

Now you can also change small, little things,

or small, little colors in that back region.

Let's say that this isn't quite what we were looking for.

Where you can increase the colors up here in the screen colors,

so let's just increase that a little bit more,

we'll exaggerate it.

So there we go.

Let's just exaggerate even further, so one five,

so we can see that it's starting to neutralize it,

but we can play around with these colors to a degree so that

we can change that backing region color.

Now if you push it too far, let's go.

5, then you can start to affect this one.

So let's go 100%, and that's definitely not going to work,

so be careful with these colors.

We really want to start to play with this backing region color 'cause

that's going to help us with our pre-multiplied images,

or once we have the final composite.

So now that we have reviewed how to do the despill with the keylight tool,

let's take a look at it with expressions in our next clip.