Canon HDSLR Footage and Alpha Layers

Not quite sure what you mean. Maybe I misunderstood.

When importing any footage that has no alpha information natively, AE "adds" opaque alpha-information.
There are several ways to add your own alpha information to the footage. Masks are just one of them. To then bake the alpha information into the footage, you'll have to render it out to a format that supports alpha channels - like Quicktime (codecs could be Animation, PNG, ...). In the render settings you'd have to tell AE to put the alpha information in (RGB + alpha).

Was that your question? :)

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Glad, I helped!

[Teresa Seito] " I was just curious if there was some magic switch that took the luma information from the color channels and then converted that info into an appropriate grayscale transparency that could rest in the alpha channel, and then be used for other purposes"

There are a couple of ways to do just that. Simplest way to use the luminance information as an alpha channel, is to apply one of the channel effects (don't know the english name, must be something like "change channels"... something like that...)
You can simply choose the luminance information as an alpha channel.

Another way is to duplicate the layer, add a b/w effect (tint, b/w, hue/saturation, ...) to the duplicate and use that layer as an obscure matte (inverted luma matte) for the original layer. IMHO the better way, because you can tweak the matte to your liking with levels, curves or whatever...

I'm sure there are still about a hundred other ways to achieve the same (or better?) results.


All the best!

------------------------------------------
"Tragedy is a close-up; comedy, a long shot." - Buster Keaton

Me on Twitter (english/german)
http://twitter.com/FastFoodVideo

My german blog
http://fastfoodvideo.de