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29 Jan
2007

Green Screen After Effects Tutorial

Chroma screen keying with Keylight in After Effects


(Update - Newer versions of After Effects have keylight already included)

Here is a tutorial covering the basics of keying using keylight in After Effects 7. If you want something that gives you the best green/blue screen keying in After Effects, then in my personal opinion keylight is it.

First download the demo of keylight at www.thefoundry.co.uk/.

You can also find example green footage here www.hollywoodcamerawork.us/greenscreenplates.html

But before I start I can't stress the importance of lighting when filming... do your very best to give a clear background colour on the film shoot.

Step 1.

Below we have the elements for the scene. Our clip of someone on a skateboard and a still image for our background.

Chroma screen keying tutorial - Picture 1

Chroma screen keying tutorial - Picture 2

Step 2.

Start by creating a new composition and call it 'GREEN SCREEN'.

Chroma screen keying tutorial - Picture 3

Step 3.

Now lets import the 'GREEN SCREEN FOOTAGE.mov' and 'BACKGROUND.jpg'.

Chroma screen keying tutorial - Picture 4

Step 4.

Place both elements on the timeline making sure the footage is above the background image. I've had to move along the timeline to get a more full shot of the skateboarder.

Chroma screen keying tutorial - Picture 5

Step 5.

Making sure that the 'GREEN SCREEN FOOTAGE' is selected, go to the menu and choose 'EFFECT/KEYING/KEYLIGHT(1.2)'.

Chroma screen keying tutorial - Picture 6

Step 6.

At first nothing changes... the reason being that keylight has a default screen colour of black, when we want green.

Chroma screen keying tutorial - Picture 7

So first thing we have to do is select the keylight filter and 'SCREEN COLOUR' option. Then go to the preview window and select a part of the green background.

Chroma screen keying tutorial - Picture 8

As if by magic the background image will appear.

Chroma screen keying tutorial - Picture 9

Step 7.

That's it... or is it? Take a closer look at the original 'BACKGROUND.JPG' and then as it is on the preview window. Something isn't right.

Chroma screen keying tutorial - Picture 10

Start by changing the FINAL RESULT option to SCREEN MATTE.

Chroma screen keying tutorial - Picture 11

We now see that the matte isn't a sharp and clear black and white, which is causing the problem with the background not clearly showing through.

Chroma screen keying tutorial - Picture 12

Step 8.

Now select 'SCREEN GAIN' and change it to '120'...

Chroma screen keying tutorial - Picture 13

... then look back at the preview window. We now have a lot cleaner matte.

Chroma screen keying tutorial - Picture 14

Step 9.

Change keylight back to FINAL RESULT. You should now see a lot clearer background behind the skateboarder.

Chroma screen keying tutorial - Picture 15

Step 10.

Before saving and rendering the clip, do a ram preview to make sure the keylight settings work for all the other frames.

Chroma screen keying tutorial - Picture 16

You may have to fine tune your settings depending on the quality of the footage, even play around with the colour settings so it matches with the backgrounds lighting.

Hope this helps.

me@grafxflow avatar

me@grafxflow


I am a Full-stack Developer who also started delving into the world of UX/UI Design a few years back. I blog and tweet to hopefully share a little bit of knowledge that can help others around the web. Thanks for stopping by!

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