Requirements: Digital Fusion
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Archive:  Printable Microsoft Word Document. (346 K)

In this tip I will outline a method that I use for most blue/green screens utilizing Digital Fusion's Ultra Keyer.

The first obvious thing would be to select the appropriate color. Blue or green?

Next I drag the matte separation slider up to get the basics of the key. Generally you will want to go far enough to remove most of the background, and still keep some of the transparency (if any.)

At this point I will begin to select areas by box selecting sections of the background that are not currently removed. (Alpha greater than 0.) Pay attention to the transparency of objects in the scene to make sure you don't push things too far. If you do remove too much, use [ctrl] + [z] to undo your color picking. Again, at this stage, we don't need to have a perfect key, just something close.

Now I will go in to the matte controls, and clip the matte. This will help fill in the holes in the foreground, and clamp the noise in the darker areas of the matte.

From here I fine-tune the spill suppression and fringe gamma over the background.

Some things to keep in mind when keying;

1. Garbage matte and roughly rotoscope what you don't need. This can help narrow the amount of keying needed on an un-even lit screen.
2. Some keys will require multiple passes. If the camera pans over one area that is lit better than another, you may need to branch out from the source footage to multiple Ultra Keyers, and then dissolve between tools.