Alpha not clean (black BG, motion blur)

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Old 03 March 2013   #1
Alpha not clean (black BG, motion blur)

Hi!

This is weird. I render my rotating object with the sky object invisible to the camera. That mean the render is on black background. However when I import it in After Effects and put the alpha setting at Premultiplied Black like it should be, I got a lot of mess around my object. Straight too of course. When I change the color to a dark grey, it get better on the edge but not on the motion blur.

Coming from Lightwave, I am use to perfect edges when using a black background.

Any way to fix that?

thanks
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Old 03 March 2013   #2
Quote: I got a lot of mess around my object.


What do you mean? Aliasing problem?

Have you tried an object buffer for the same object and compared with the alpha? Is there a difference ?
 
Old 03 March 2013   #3
Did you set the Alpha channel in C4D as Premultiplied?
you do that by unchecking the "Straight Alpha" checkbox.
If you set your Alpha to Straight, C4D creates a "bleed" around the objects and the Alpha channel works perfectly, but you have to set AE to use Straight as well

It is better workflow to work in Straight Alpha, anyway.

Once again, PLEASE post an image or something.
A "mess" means nothing.
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Old 03 March 2013   #4
Thanks Noseman, yes it was that. I forgot to update my post (rush rush job) but fixed it when I discovered (after googling a lot) the straight alpha switch. After that, the alpha was really clean.

Thanks a lot!!
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Old 03 March 2013   #5
you are welcome...
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Old 03 March 2013   #6
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