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Combustion Eye for the AE Guy

Part 4: Keying in combustion 3 By Stephen Schleicher

The AE user should already know a fair amount about keying in After Effects.  As you make the migration to discreets combustion, you will find several new ways of pulling a key from a blue or green screen shot.  In this installment well examine how keying in combustion works, and how to use combustions Discreet Keyer for your next project.

Combustion contains a variety of keying operators.  The Difference Key Operator works the same way AEs Difference Key does not that well for footage with a lot of grain.  You may find a use or two for this one when you are in a tight spot, but your results will often be sub-par. 

The Linear Key Operator is a plain and simple keyer that uses a color range to remove the green or blue background.  While this is a simple operator, dont let its name fool you.  If you have a solid background, a foreground subject with no transparency (glass, hair, etc.), this may be the best keyer for your job.

The focus of this article is the Discreet Keyer and how it can be used in your workflow.  For this example, I will be using a subject against a green screen captured in the DV format.  I am using DV footage as it seems most of the requests I get on keying revolve around doing it in the DV space.

It needs to be pointed out that trying to pull a key with DV footage will be an exercise in patience.  While you can pull a good key, it will not be a great key.  Because of compression and artifacts that arise with the format, you will find it difficult to retain the fine details (wisps of hair, fur, etc.) and clean edges in the final key.  Discreet Keyer does a good job of pulling a key with DV footage.  For really stellar results you should use an uncompressed format.

Step 1:  Create a New Workspace.  Import your green screen footage and background clip.  In this example, the talent will be keyed over a video clip provided by Artbeats (www.artbeats.com) from their Time & Money collection.

Step 2:  As you can see in the above image, there is a lot of ?stuff around the green screen.  Since the subject doesnt move, and we know we dont need said ?stuff in the final shot, Ill use a garbage mask to rough out the area we want to keep.  In combustion you can use the Draw Mask operator to either drop anchor points or draw out the mask shape.  With a garbage mask, remember to keep it fairly loose.  If the actor moves, you will need to animate the garbage mask to match.

When it comes to animating a garbage mask, users tend to think they need to animate the mask every frame.  For a good article on the popular Bisecting Animation technique used for masks, check out the article I have written that discusses the concept.  The technique will work in any application that allows you to animate a mask shape over time.


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Related Keywords:discreet, combustion, keying, after effects, schleicher, tutorial, exercise, workflow, discreet keyer, compositing, matte


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