By now you may or may not have built your own blue/green screen set using one of our many "How To..." tutorials. If so, the next logical step would be to do some green/blue screen removal so let's give it a go!

This type of work is referred to by several terms: keying, colour keying, chroma key, blue screen removal, green screen removal and so on. All these things are the same thing and for arguments sake the word "keying" works just fine by itself.

For this tutorial you are going to need to obtain a copy of Adobe After Effects (at least version 5+). Once you have "obtained" your copy, then read on.

COLOUR REMOVAL

1. You need two different elements for this example: your foreground and your background. Here you can see in our foreground that our person has been shot in front of a green screen (don't forget green screens don't have to be green - blue is just as popular!). For our background plate, we have a still image of a waterfall but again you can use whatever the hell you like including live action footage.

Our objective is to make it look like our lovely lady is standing in front of this waterfall!

FOREGROUND - GREEN SCREEN	BACKGROUND PLATE

Import these two elements into the After Effects composition timeline, each on different layers.

2. Select your foreground layer in the timeline and apply a keying effect so we can remove the green screen. This can normally be done by clicking on the layer, then pressing the right mouse button and making a selection from the menu. I would suggest using "Colour Key" (your AE version may have different options but it is usually found at effects>keying>color key). Then using the eye-dropper tool in the effects control box that should pop up, click on your green screen in the preview window.

This tells After Effects that this is the colour you want to remove. Now, you may need to tweak the settings a little such as colour tolerance (the higher the number, the more green that will be removed). I would suggest messing around with the settings so you can see for yourself what they actually do. After all, you can just click undo if things f*** up.

3. You may find that the person you have filmed has a light green edge (or blue edge depending on the screen colour you used) around them. You can use After Effects built-in colour suppressor and/or linear key tweaking. Experimentation is the key if you'll pardon the pun!

AFTER COLOUR KEY	AFTER LINEAR KEY/SPILL SUPRESSION TWEAKING
FINAL COMPOSITE

And that's it. How quick was that?!!

DIFFICULT KEYS

Of course, not all keys are simple and some can be a right nightmare to fix. Imagine video footage of that woman seductively flipping her hair back in front of the green screen. Sexy? Yes! Easy to key out? No! What if she was wearing a green dress at the same time whilst sitting inside a car with very reflective mirrors which were bouncing light from the green screen all over the place? A pigging nightmare that's what it would be.

Click here for our list of tips on producing good quality keys by avoiding the typical mistakes of amateurs (link coming soon)

For more advanced guides to keying, I would recommend doing a google search as it is a knowledge haven! I will eventually put some more keying guides up on this website but for those can't wait, google is your friend.