Original subtitles

In this clip we're going to take a look at green screen keying QC checklist.

So a QC checklist is a quality check checklist and we want to use

this so that we can make sure that we have all the fine details

needed to take this particular image to final.

So let's take a look at the first item.

So the first item is alphas.

So are the core alphas opaque where needed?

So we want to make sure that there are no holes in our alpha and to do

this we're going to color slam the LUT to QC our image.

So color slam the gamma up and down to make sure that

there are no holes in our core alpha,

but also to make sure that there isn't too much information

or artifacting in our backing region.

Next, we're going to see if there is any buzzing in our alpha.

So we want to make sure that there is no buzzing because those

really create unstable edges and as a result it doesn't have a

very good output for our final composite.

Next we're going to take a look at order of operation.

So we want to make sure that we have the correct order

of operation for color correction.

So color correction should be done on premultiplied images.

So if you have a premultiplied image, be sure to un-premultiply it first,

complete your color correction, and premultiply it,

and this really helps to retain all the information in our edges.

Next we looked at optimized concatenation.

So we want to make sure that all of our transform tools are

grouped together in the same location.

Don't break them up with non-concatenating tools.

If we do so,

we can actually introduce lowered resolution or lowered details in our image.

So we want to retain as much detail as possible so

keep all transform tools together.

Next we looked at correct round-tripping.

So it's very important to round-trip our images back to the original state.

So an example of this is moving from linear color space into log,

perhaps completing a key,

and then round- tripping back to that linear color space.

So just make sure that when you are doing these operations,

that they are round-tripped correctly in order to continue on with our comp.

Next we're going to take a look at edge details.

So are all the edges, the transparency,

motion blur and wispy details retained in comparison to the original plate?

So for example, if we don't retain that information,

it's going to be harder to convince that this wasn't a green screen image.

So we want to retain that information so that it looks like

it's better integrated into our final plate.

Next we're going to take a look at despill.

So has all the spill been correctly removed?

So we want to make sure that any light-colored skin isn't accidentally changed,

that the blonde hair isn't turning magenta,

and that any light-colored materials or clothing hasn't changed as well.

So make sure that we are retaining the color information that we need

and that we haven't pushed that despill too far.

Next we take a look at has the despill been completed

separately from the final alpha.

So this is really important when it comes to advanced keying.

Basically we don't want to have any patchwork quilt-like images from

completing the despill and the keying together in one step.

So make sure that all of your color correction and your despill is

completed on the plate separately and that the alpha is applied

after the fact for the final composite.

Next we take a look at artifacting.

So are any artifacts still visible?

So for example, in the backing region.

So 5% opacity in the backing region is a good place to start.

It doesn't always work.

So you might have to drop it below that 5%,

but just double check with your background image to see if

it's visible and if it's causing any issues.

And of course, we're going to take a look at final integration.

So does the color in all the elements match?

So does the foreground green screen element now match with the new background?

Does it look like it's taken in the same location?

So this is really important in order to convince the viewer

that this is a non-green screen image.

Does the green screen noise match all of the remaining assets?

So we want to make sure that we take the noise from the green screen image,

we retain it, and then we match all of the elements surrounding it to that noise,

again so it looks like it was all taken in the same plate.

Does the green screen image's focus match that of the remaining elements?

So maybe we take the green screen image and that's going to

drive the focus of the rest of the shot.

So if that is the case,

just make sure that your new background image matches

the focus of your foreground image.

Comp optimization.

So have all unneeded tools been removed, disabled, or pre-comped?

So this is very important because we want to make sure

that this comp has been optimized, that it is running as smoothly as possible.

So unneeded tools can slow down your composite.

It can become very confusing for other artists that pick

up your script and elements that are not pre-comped can

actually slow down your script.

So for something such as pre-processing,

that's a really great thing to pre-comp,

bring it in as a new image sequence,

again just to optimize and speed up your comp.