- [Narrator] Color correcting is, of course,
a vital function for compositing visual effects,
so Nuke has a long list of powerful color correcting tools.
They're located right here on the color tab.
The most important of these tools are the Grade node
and the ColorCorrect node.
Here we'll see what the difference is between them
and when to use them.
We'll start with the Grade node.
We'll select the read node, come up to the color tab,
pop it up and we'll find our Grade node right here,
and it's so important, it gets its own little
keyboard shortcut, the letter G.
So, we'll pop that puppy in there
and take a look at what we got.
Now let's look at the adjustments in the Grade node first.
The blackpoint, whatever code value
is put in here is pulled to zero.
The whitepoint, whatever code value
is put in here is pulled to 1.0
Now, the lift, gamma and gain are identical
to the lift, gamma and gain of a standard color corrector.
The multiply does the same operation as gain,
it scales RGB values up and down,
and the offset simply adds a constant
value to the entire frame.
Okay, so how might we use the Grade node
to do a preliminary grade on a film scan?
Alright, so we'll take a look at this
film scan here and this is a log film scan dpx file format
and it is horribly over exposed
and got a heck of a red tint to it somehow,
so we're going to have to fix that
with a preliminary color grade.
So, I like to start with a blackpoint
which will affect these dark areas here
and down here.
So, the blackpoint then, I'm going to raise
the blackpoint code value until I get that to look nice.
Remember this is what'll be pulled down to zero.
So, if I raise this up, that part
of the picture goes dark.
Okay, let's rehome the viewer.
Okay, the whitepoint.
If I pull the viewer gamma way down, we can see that
I have an awful lot of clipped pixels up here.
So I really want to get those pulled inside
between the zero and one values,
so I'm going to have to bring down
the code values, so in other words,
I want to put in a whitepoint, a high number,
that will bring those down to 1.0 until it looks pretty.
Okay, alright, so now let's see, how did I do?
Okay, I've still got a little patch up here,
but that's okay- we'll have a little
tiny bit of the picture that's clipped,
but see all this red?
No, I think that's from that red over-exposure,
look how red that picture is.
So, we'll fix that next.
We'll try doing that.
We'll open up the gain property panel here
and let's take our red code value down
until we get rid of all that excessive red.
Ah, there we go! Okay.
So this is what the film scan
should've looked like when it came off the film scanner,
but it didn't, so we fixed it.
Key point, you must do a preliminary grade
on all your camera raw footage
before it goes to visual effects.
You cannot give them this picture
to apply visual effects to, okay?
Alright.
Let's go look at the ColorCorrect node over here.
The ColorCorrect node is designed to visually match
one image to another, as in a composite,
by adding zone controls to individually adjust the shadows,
the midtones and the highlights.
The mission is different.
We're trying to match two images.
For example, this keyed green screen foreground here,
over that background there, as a composite.
So we need much more delicate control
over different parts of the picture,
hence the zone control in the ColorCorrect node.
Alright so we'll select this read node from our foreground,
come up to the color menu, and we'll pick a
ColorCorrect node which has also got its own
keyboard shortcut, the letter C.
Hook that puppy in.
So I'm doing a color correction on the
green screen foreground here, before it's composited.
Okay so let's take a look at our ColorCorrect node,
and how we might use that to match these two layers better.
It doesn't really matter but I like to start in the shadows,
in the darks.
Look what happens if I pull the viewer gamma up.
See the black underside of these shoes?
That would be the darkest point in the picture.
They're much lighter than these blacks
back here in the background,
and I want those two to match each other.
So I'm going to go to the shadows, right here,
take the gain, and gain down just the shadows
until I get a good match between my shoes
and the background plate.
Okay, much better.
Next, let's take a look at the flesh tones here.
Oh these are horrible, look at that.
They're all green and sallow and pale.
It doesn't matter what color the clothes are,
the skin tones must be correct.
The audience will immediately know if the skin tones
are not right, so you have to get the skin tones right.
Now these skin tones are in the midrange,
so we'll look at the midtones here,
and I want to pull green out of the midtones.
So I'm going to select the gain,
and I'm going to start pulling green out of the gain.
There we go.
Now these are much healthier, fleshy looking skin tones.
Okay, next let's hit the highlights.
Let me pull the viewer gain down here
so you can see this highlights thing work.
If I grab the gain control of the highlights,
you can see it's only hitting
the very highlights of the picture, okay?
That's the zone we're working in here.
Now what I wanted to do was I wanted
some more blue in those highlights,
let me bring this up just a scoche here.
So, if I want to add some blue to these highlights,
I'll come down here to the gain,
and I'll start cranking up my blue,
and let's say I like that.
Okay, so I've added some blue into these highlights.
And we'll set the viewer gain back to normal,
and rehome the viewer.
Okay, so I've dialed in my shadows, midtones and highlights
and now we can look at the master control,
again this is kind of like the Grade node
in that this in the entire picture, okay.
No zones here.
So, my problem is, you see this background umbrella here?
You see how warm those whites are?
So I need to warm up my ladies,
so we'll go to the master control, select the gain,
and let's take some blue out of the picture.
Ah, there we go, now they look a lot warmer
by removing the blue.
Rehome the viewer.
And looking at 'em in context,
I think they look a little too saturated.
So we'll come up to the master saturation,
and drop that down a couple of points.
Okay, so zone control.
Shadows, midtones, highlights,
and of course the master control.
You need all of this extra control,
because matching two layers like that
is much more complicated than just
doing a preliminary grade on a plate.
The other thing you should be aware of is the ranges tab.
This is where shadow, midtone and highlight are defined.
I'm going to just pull up the shadow curve.
So the shadow only goes from 0 to 0.09.
Remember, we're working in linear lightspace,
so all of our code values are really very small.
If we look at the highlights,
the highlights start at 0.5.
Now if you were working on an SRGB image,
that would be right in the middle of your midtones,
wouldn't it?
Alright so if we look at the whole thing,
what happens is you define the shadows and the highlights,
and Nuke creates the midtone curve out of the results,
you do not adjust the midtones.
So watch this.
I'll move my shadows, and there goes the midtones.
I'll move my highlights, and there goes the midtones.
Ah let's undo, undo, cause I'm messing up
my beautiful picture.
So use the Grade node to do a preliminary grade
on a camera raw plate,
and the ColorCorrect node for matching two layers in a comp.
Of course, the Grade node can also be used
for simple color corrections as well.