Footage and alpha channels

[Mike Clasby]

I’m no expert, but that’s what keying is all about, adding transparency to colors or luminosity:

Color Key

“Keylight” is very powerful and a separate instill of the disk I think.

Knoll Unmult (A FREEBIE):

https://www.redgiantsoftware.com/unmult.html

KNOLL UNMULT
Knoll UnMult is used to generate mattes for light effects or other bright elements generated on a black background. It is also the perfect solution to cleanly composite elements with pre-multiplied alpha channels.

UnMult creates an alpha channel based on the maximum luminance of the RGB channels. It also makes the RGB channels “un-premultiplied”, giving you full access to the RGB values of an element without any alpha-based attenuation.

Aharon has some tuts on Alpha:

Understanding Straight vs. Premultiplied
https://library.creativecow.net/articles/rabinowitz_aharon/straight_vs_premult.php

He uses Keylight, here;
Creating Super Tight Junk Mattes
https://library.creativecow.net/articles/rabinowitz_aharon/junk_mattes.php

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[Stuart Fellows]

Thanks Yikes, you gave me quite a bit to look into. I realized after I posted that AE creates an alpha channel regardless but it’s generally all white. So that was the differentiation as to what I’m looking for. Anyway I’ll pursue these links and tutorials.

Cheers
Stuart

[Richard Harrington]

Calculations or Set Channel effects

Richard M. Harrington, PMP

Author: Photoshop for Video, Understanding Adobe Photoshop, and ATS:iWork

[Stuart Fellows]

Thank you Richard. Over the past few weeks I’m been brushing (no pun intended) on my masking skills in photoshop, so I now know that I can carry those over to AE.

However, in addition one tool that seems interesting is Matte Generator from Digital Film Tools. I haven’t seen anything around though that demonstrates the product except for a small photo on the DFT website. I kind of wonder why no one has a done a tutorial on it. And I’m not volunteering, at least not yet 🙂

Stuart