This week I’ll show you 5 ways to make your green screen composites look actually good.
And not bad.
Keying is only ever the first step of compositing a green screen shot.
In fact, any good visual effects shot will always be a multi-step thing.
The more detail you put into a shot, the better it’s going to look.
Here’s a vlogger we filmed on a green screen.
I’m going cover how to turn this into THIS.
Or this.
Or even this.
The important thing is that although I’m dealing with a pretty simple example here
- a green screen presenter with a composited background - the techniques apply to any compositing
you’re doing.
This is about how you bind your layers together.
As a note, most of what I’m talking about here requires effects found in HitFilm 4 Pro
or HitFilm Express add-ons.
You can find full details in the video description.
OK, I’m going to set up my background.
I’ve got a bunch of images imported, so I’ll drag one of those underneath my keyed
layer.
As you can see, although we have a clean key it doesn’t look like the two layers are
part of the same shot.
I’m first going to select my background image and convert it into a composite shot
using this button on the timeline.
In the window that pops up, I’ll switch from current layer to timeline, so that the
new composite shot has the same properties as our main one.
After clicking OK you can see that we have a brand new composite shot timeline with the
image moved inside.
Whatever is on this timeline will show up as our background, which will save us some
time later on.
OK, so you’re probably all familiar with spill suppression.
This is the method used to minimise light spilled over from the green screen.
We're also going to cover something called spill replacement.
[EXAMPLES WITH VO] So here’s what spill suppression does.
You start off with your green screen clip.
This dog is a great example because his pale coat REALLY sucks in all that green spill.
It’s not super obvious when the green screen is still there, but once the green screen
is removed, you suddenly notice there’s a ton of green light over the image, especially
under the dog’s chin and on its chest.
Spill suppression is designed to neutralize that green spill.
Switching to the Despill map view shows exactly which parts of the image are going to receive
spill suppression.
For this fella I’ll increase the hue range to 0.32 so that all of that green fur is included.
OK, so watch as I adjust the amount of spill suppression.
Here it is with NO spill suppression - and there’s a ton of green.
Now as I increase the spill suppression, note how the green disappears and turns to a neutral,
natural color.
HitFilm goes one further with something called spill REPLACEMENT, which doesn’t just neutralise
the spill but changes it from one color to another.
So by default HitFilm is neutralizing spill to a mid-grey.
But I could drop in my sunset sky background and change the color to one of these deep
reds or oranges.
And for a background that’s fairly uniform in color that’s great.
But what about something with more variation?
Even in this example, do I go for the dark reds, the oranges, or the yellows?
Well, that’s when you simply select a source layer, and let HitFilm figure it out.
This creates a variable spill, based on the background.
And it’ll update even as that background changes or is moved around.
Light wrap is brilliant.
It replicates a subtle but vital consequence of positioning an object in front of something
bright.
In the sunset example there’s a really bright sun in the background.
But without light wrap, there’s no interaction between the layers.
This causes the background to look more like a painted backdrop, rather than a sun blasting
out light.
I’m going to find the light wrap effect and add it to the composited layer.
I’ll then set the source layer to the Background.
Immediately it makes a difference, with the background colours bleeding into the foreground,
but without losing the edge definition.
I always switch the blend mode to Lighten because it creates a more realistic result.
For this particular shot I’m going to increase the radius to about 60, which is big but works
in this case.
I’ll then drop the opacity down to about 0.8 so that it’s a bit subtler.
If I turn the effect off and on, check out the difference it makes.
So with it on, there’s all this light bloom going on around the sun and bright patches
of sky, while nothing’s really happening around the darker areas.
Although the difference is REALLY obvious when I’m switching it on and off like this,
once it’s on it very quickly disappears into the image and just looks natural.
Thing is, when you’re combining multiple layers together it’s quite likely that they’re
from different sources.
In the example I’m using, we shot the vlogger on an FS700, while the sunset image is a random
picture I found in a quick Google search which was shot on a stills camera.k
Even if the same equipment is used, elements are likely to have been shot on different
days or locations under wildly different lighting conditions.
If you want a shot to look natural, you need to grade the layers to match each other.
Let’s take a quick look at our layers.
If I add the Levels Histogram we can get a simple read-out on what the layer looks like.
Our keyed layer has a nice range of color values and a decent contrast range.
Whereas our background is super minimal, with everything in the red channel and peaks at
the bright and dark ends of the spectrum and not much in the middle.
So back on our foreground layer, I’m going to adjust the contrast so that she also has
nice, solid blacks.
And that’s just instantly better, with just one tweak.
There’s all kinds of ways of adjusting contrast in HitFIlm - check out my previous video for
some more info.
An interesting way of matching the looks of multiple layers is to use the Grading Transfer
effect.
This does what it says on the tin, applying the look of one layer to another.
Let’s give it a whirl.
After adding it to the foreground, I’ll go in and select the background as the reference
layer.
WOW.
So that’s really intense.
But you can immediately see what’s going on.
And at this point, let’s make use of our background composite shot.
I’m going to jump over to the background comp, and then drag in a different image.
Maybe this nightclub scene.
Switching back to the main composite shot, you can see that the grade transfer has updated
based on that new background.
Again, this is a super extreme example but you get the idea.
Let’s make it a bit less crazy.
In the Global settings I’ll drop both the brightness and chrominance shifts down to
0, then gradually increase them until I get something I like.
I’m pretty happy with the overall brightness of the foregroud, so I’m only going to put
that up to about 20%.
What we really want is to match those colors, so I’ll boost up chrominance.
So in this case, although my instinct is to whack chrominance shift way up, it actually
works pretty nicely around 20% again.
This still looks NATURAL, which is what we want, but it blends those layers together
really well.
The funny thing is that your eyes have probably already adjusted to it, so it’s kinda hard
to tell if the effect is even making a difference.
But check out what the original looks like with Grading Transfer turned off.
That is one major change, which perfectly captures the lighting of the background.
If I go back and swap out that background again, then go back to the main comp, you
can see it just works.
Generally speaking, cinematographers have spent decades trying to figure out how to
avoid unwanted visual aberrations like anamorphic streaking, light flares and dirty lens.
Ironically, visual effects artists have now spent a comparable amount of time trying to
figure out how to CREATE those exact same things.
And the problem with digital visual effects is that that tend to look pristine and perfect,
and real life ain’t that.
By adding some deliberate ‘errors’ into your VFX, you have the side effect of making
them look like they were shot under real conditions.
We’re going to be adding lighting and flare effects and we want to make sure they apply
to the whole shot.
For this we’re going to need a Grade Layer, which I’ll add by going to the New Layer
menu down on the timeline.
Grade layers are handy because they affect everything underneath them.
To this I’ll add light streaks, which requires a bit of setting up.
First up, switch the blend to Add, so that it mixes with the other layers.
It’s then a matter of adjusting the settings to get the look you want - I’m going to
put the threshhold way up, so that only the very brightest parts of the image generate
streaks, and keep the brightness and size relatively low, so that it remains a subtle
effect.
If I switch it on and off you can see the difference it’s making.
This gets interesting when the foreground layer goes in front of the bright areas.
This automatically updates the streaks effect, and makes it look like the presenter is interacting
with the background lighting.
This is all about simulating what you might capture through a lens if you’d shot it
for real.
The anamorphic lens flare effect can be used for a similar purpose, mixing the layers up
so that they appear to be interacting with each other.
I’m going to adjust the streak here to be horizontal and turn off pivoting, so that
the streaks are directly connected to the source.
Again, I’ll keep the threshold pretty high so that only bright areas are generating the
flaring, and I’ll blur it out and drop the intensity down.
The result is a subtle light streaking across both layers.
It should be emphasised that this stuff is all optional and subject to taste, and it
won’t work for every project and every story.
There’s a ton of effects in HitFilm that are useful for this kind of thing.
Lens dirt and light flares can also work wonders - I’m using an auto flare in this sunset
shot, so that there’s a nice glow coming off the sun which still gets obscured when
her hand goes in front of it.
When you determine the final look of your movie, you’re creating a unified look across
the whole frame.
This helps your visual effects shots as it makes everything in the frame look like it’s
from the same source.
I tend to put another Grade layer above everything in the scene, and use that to do the final
grade.
This is obviously dependent entirely on the specifics of the shot, but just to demonstrate
the concept I’m going to take a shortcut and slap on the cine style effect.
Obviously in a real project you’d want to take more time to fine tune the look, probably
using a combination of multiple effects.
The point though is that unified adjustments to contrast and color have really helped to
make this shot look real.
The letterbox bars contribute as well, introducing a visual framing which encourages viewers
to regard it as a single shot.
Cine style even adds grain across the whole frame, which is a subtle way of telling an
audience’s eye that it was all shot on the same stock.
So by following these 5 tips we’ve gone from our original green screen shot and the
initial, basic comp to a version which looks far more convincing and natural - albeit in
quite a stylised form, in this specific example.
A lot of the stuff I’ve talked about in this videois really subtle.
But if it wasn’t there, they’d instinctively know that something was wrong, even if they
didn't know what exactly it was.
The holy grail for many VFX shots is that, after all the hours of work you’ve put in,
absolutely nobody watching even notices.
And when that happens, you know you’ve done your job properly.
Many thanks for watching as always!
Kirstie and Josh are back next week so make sure you hit the GIANT subscribe button to
make sure you don’t miss any episodes.
Hey guys it's Kirstie here!
I just wanted to jump into Simon's episode to let you know that we've got a sale going
on - 15% off HitFilm 4 Pro until the 1st February 2016.
So if you want to get your hands on the software, now's the time.