ADOBE AFTER EFFECTS: Forum Expressions Tutorials Creative Cloud

Straight Alpha Channel on AVI

COW Forums : Adobe After Effects

<< PREVIOUS   •   FAQ   •   VIEW ALL   •   PRINT   •   NEXT >>
Milos RistoskiStraight Alpha Channel on AVI
by on Aug 9, 2016 at 11:25:44 am

I'm trying to render some logo animation with feathered circle in the background. When I render the AVI I get the same results with straight and premultiplied. In Sony Vegas for example there is difference. If you select the straight alpha you get black feather on semi transparent edges, that is the effect I want to achieve.


Return to posts index

Walter SoykaRe: Straight Alpha Channel on AVI
by on Aug 9, 2016 at 4:09:39 pm

When alpha is interpreted correctly, you don't get fringing at all, whether you're using premultiplied or straight. You DO get black fringing in transparent areas when you render with pre-multiplication, but interpret as straight alpha.

If you want to use this to creative effect, just use Interpret footage [link] to change the alpha interpretation.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


Return to posts index

Milos RistoskiRe: Straight Alpha Channel on AVI
by on Aug 9, 2016 at 5:21:39 pm

Yes, but when I render the AVI file with premultiplied alpha, I don't get to choose the type of alpha channel in Premiere Pro when importing.


Return to posts index


Walter SoykaRe: Straight Alpha Channel on AVI
by on Aug 9, 2016 at 6:29:41 pm

[Milos Ristoski] "Yes, but when I render the AVI file with premultiplied alpha, I don't get to choose the type of alpha channel in Premiere Pro when importing."

Premiere Pro has an Interpret Footage dialog you can use, but it's a bit less flexible than Ae's, so it's not as easy to assign the incorrect alpha interpretation.

To get the "wrong-alpha fringe" from Ae to Pr, try rendering both an RGB pass (normal, premultiplied color) and a separate Alpha pass (add an output module and choose "Alpha" instead of "RGB" or "RGB+Alpha"). Import both movies into Premiere Pro and use Premiere's Track Matte Key effect to to pull a luma matte from the alpha pass.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


Return to posts index

Milos RistoskiRe: Straight Alpha Channel on AVI
by on Aug 9, 2016 at 10:11:44 pm

Thank you, but I found a more simple solution. I rendered the animation in Targa sequence.


Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2017 CreativeCOW.net All Rights Reserved
[TOP]