All language subtitles for 4. White Balancing and Color Correction

In this clip, we are going to take a look at white balancing.

In the previous clips, we took a look at denoising the plate first.

So it's really important so that we can retain the details in our keys.

So the second part is of course white balancing,

and that's another preprocessing step that we can take.

We're going to take a look at a couple of different terms that

is going to help us with the white balancing.

The first one is color cast.

So color cast in a tint of a particular color,

usually unwanted,

which affects a whole or portion of a photographic image evenly.

It can be caused by colored gels or filters that are placed

over top of the lighting used on sets,

and they are sometimes used to create a mood.

So for example, blue lighting creates more of the cooler tones,

and yellow or magenta creates more warmer tones.

Other color casting can be caused by improper white balancing on set.

So what exactly is white balancing?

White balancing is the process of removing unrealistic color

casts so that the objects which appear white in person are

rendered white in your photo.

So for example down here we have a woman that has a white cardigan,

and it doesn't quite look white in this piece of footage.

So that's partially because of the green spill onto the character,

but it's also because perhaps the white balance wasn't quite right on set.

Proper camera balance white balance has to take into account

the color temperature of the light source,

which refers to the relative warmth or coolness of the white lights.

So let's take a look at what color temperature is a little bit more in depth.

So color temperature is measured in Kelvin, or K for short.

The Kelvin scale ranges from 1, 000 for the measurement of candlelight,

to 10, 000 for an overcast sky.

Those are just approximate numbers, of course.

The scale starts with the warmest color casts, and it ends with the coolest.

So just those reference to most of our footage for these modules and clips,

and that is that we filmed mostly with either tungsten or daylight lighting.

So tungsten lighting is approximately 2500 to 3500K,

and daylight lighting is approximately 5000 to 6500K.

So now that we've reviewed a number of different terms,

let's take a look at what it looks like in person.

So back to our images, and we have a character cropped in nice and close for us.

And let's take a look at some color cast.

So here's the original image,

and we have artificially introduced a cool color cast.

So it changes our character, it changes the green screen.

So overall, they look very blue.

So this newspaper is not looking quite right.

The skin tones are looking very pale.

And so this is very, very unrealistic.

We definitely need to change it.

And then there's the opposite in the scale, which is the warm color cast.

And again, it changed the green screen so it may be harder to pull a key.

But definitely, we can correct it.

So let's take a look at our workflow.

So we have a woman on the green screen,

and again we've introduced an artificial cool color cast.

And this is just for this particular example.

And first up, of course, is denoising the plate.

So denoise that plate.

If you need a refresher,

please go back to the clip from earlier in this module

to learn how to do that in detail.

Next we're going to pull a keylight.

So here's a keylight that I pulled previously.

And take a look at the alpha.

So the backing region over here is definitely way too high of an alpha,

it's between 15 and 25.

So not acceptable, it will need to be revised.

And if we color slam the lut and going down, we have holes in our alpha as well.

So definitely not final,

hopefully we can find a better solution and pull a better

key once we correct that color casting.

So on to our next step, which is the initial white balance.

So we're going to go into here and reset our values

back to one and sample the image.

So here is our initial image,

and we want to select an area of this image that should be pure white.

So what would look white on set that isn't looking white right now?

Now I could select the screen left shoulder,

but I selected the screen white shoulder previously,

and we'll see why in a moment.

So it doesn't matter which one we choose,

but in this particular example I chose that one.

So double-click on a Grade tool,

which is attached to my original footage and selects

the eyedropper for the white point.

I'm going to hold down Control + Shift + left mouse button and

drag and select that screen right shoulder.

And right away, just deselect your eyedropper,

Control + Shift + click to get rid of that red box,

it's looking much better already.

So this is before and this is after.

So it's corrected.

However, look at the difference in the luminance values.

Look how much brighter our image is, and we don't want that.

It's almost blowing out the values in the shoulder screen left here.

So there is a way to fix that.

So we will go on to the luminance matching by eye.

So I've taken a previously color corrected image from

an initial white balance over here.

We're going to work with it.

So the first thing is I'm going to look at the white option

up here at the top of the properties bin,

or sorry, on the top of the viewport, and eye view one,

hit the number two and select the wipe version,

or wipe option.

So here's the wipe option here and I'm going to wipe back in forth.

So screen left is going to be the original image.

Screen right is the corrected image.

However, it's much brighter.

So hit Y on your keyboard, which will give us the luminance values.

So I'm just going to make this a little bit wider so we can see there.

So it's showing us the luminance values.

We can also see the luminance values down here under L, under the viewport.

So with the Grade tool selected,

with the white point already selected from our previous step,

we are going to adjust the gain values.

The idea being is that we are going to try to match the values on the

screen left on the screen right by adjusting the gain.

So if I pull down the gain, you can match it pretty close.

Just pull it back just a little bit.

Now I am matching it by eye.

You'll notice that it doesn't necessarily match on

the other portions of the plate, but it's pretty darn close.

So it's looking a lot better than it was before.

So hit A twice, A, A, and it takes it to full color.

And the luminance matches much better now.

So the shoulder isn't so blown out, and we're back to where we were before.

Now if you don't like matching it by eye and you want to match it by a number,

there is a solution.

So again, let's go back to the color-corrected version from before,

or the white balance, and double-click and hit one.

And I'm going to adjust the numbers so that we can see how that works.

So sorry, we're going to hit the original image, one.

Two for our white-balanced image and hit Y so that we

can get back into the luminance.

And I'm going to sample some numbers.

So I'm going to sample up on the cheek here.

So Control + Shift + left mouse button and drag.

And our luminance values here,

I'm just going to turn off the wipe so it's not confusing.

And we can see that our original image values,

just make sure that we are viewing it, are approximately.

158.

So I'm just going to add a sticky note here and write that down.

So.

158,

and that's going to be our target for trying to match

the luminance in that same area.

So now view our white-balanced image,

and we're going to try to get the luminance values in here,

which are currently.

267 to be.

158.

So that's where it was before, and that's where it currently is.

So we're going to double-click on our White Balance tool and again,

play with our gain values until the luminance values get to.

158.

So I'm going to bring it down.

There we are, oh, we went a little bit too far.

158.

So now if we take a look at the two of them,

this is before and this is after, and it's matching pretty close.

Not quite 100 percent, but it's looking very,

very close and definitely acceptable.

So again, Control + Shift + click to get rid of that red dot.

Go back, A, A twice to full color.

And this is our original image, and that is our corrected image.

So it looks much better than it was before.

If anything, it looks almost a little bit warm.

But again, we've reintroduced the color into our character,

which is really nice.

So now let's take a look at the difference between what it

looked like before with our key and currently.

So here's our test and go A for Alpha.

So this is our original image.

And this is our corrected, white-balanced image.

So we're going to focus up here on the umbrella.

A little bit wider.

And so this is the original image and our corrected one.

So we're already adding more detail.

Look what's happened to our core.

Much, much better than it was before.

So not perfect, but just a little bit of change is introducing more detail.

Now there's one last step that we can take,

which is sometimes saturating the plate will help enhance this step more.

So just be mindful, this can be dangerous.

It can actually work against you.

But try it, and if it makes your key a little bit better, use it.

So I've added a Saturation tool before the key that I've just pulled

for the white balance and luminance matched image.

And under Saturation, I have selected green.

So we're just going to saturate the green channel,

and I've saturated it by about 25 percent.

So this is before, this is after.

It's very, very subtle between the two of them.

But let's see what it does to our key.

So let's just pull this wide one more time to see it and go into A for alpha.

So this is the white balance plus saturation and the regular white balance.

And look at the difference, look what it's done to our umbrella.

So we've reintroduced just a tad bit more detail,

but enough that it might be usable.

So it's working for us in this case.

Again,

it might not work in all cases but it's worth trying to see if it will help.

So as a quick recap,

be sure that you white balance and reintroduce that

luminance as part of your preprocessing step.

And that's really only needed if color casting is present.