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How do I blur the edges of the alpha?

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Kevin CaminHow do I blur the edges of the alpha?
by on Apr 25, 2012 at 8:53:48 pm

I have some keyed out footage, but it looks a little too crisp around the edges. I want to just slightly blur the edge a pixel or two. I've tried Channel Blur, but it leaves a hard outline.

Thanks.

Best regards,

Kevin Camin


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Dave LaRondeRe: How do I blur the edges of the alpha?
by on Apr 25, 2012 at 9:05:15 pm

Is this "crisp" as in "the subject's edges are kind of jagged and need repair"?
Or is it "crisp" as in "the subject doesn't really look like it belongs in the shot"?

If it's the first AND you did the keying in AE using Keylight, there's an adjustment right in the effect to do what you want.

If it's the second, you may not have to blur the edges: you might be able to use a trick called light wrap:
http://library.creativecow.net/devis_andrew/AE_Lite-Bite_Light-Wrap-Effect/...

Give it a shot, and see if it helps.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Tudor "Ted" JelescuRe: How do I blur the edges of the alpha?
by on Apr 25, 2012 at 9:13:44 pm

You can try Matte Chocker- it takes a bit of tweaking but the results are pretty good.

Tudor "Ted" Jelescu
Senior VFX Artist


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Chris ButtacoliRe: How do I blur the edges of the alpha?
by on Apr 26, 2012 at 8:32:56 pm

Hey, Ted - is that related to matte-chocker-full-of-nuts coffee?? :)

How about using the keyed footage as a track matte layer and just bluring that with fast blur. It will need to be pre-composed first, I believe.


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Marc NiborRe: How do I blur the edges of the alpha?
by on Feb 14, 2016 at 4:44:16 pm

Thanks Ted!
already 4 years old - but exactly what I needed right now ; )



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Andrew SomersRe: How do I blur the edges of the alpha?
by on Apr 25, 2012 at 9:51:43 pm

Here is yet another method:

Apply a BLUR to the ALPHA, and after the blur, add a LEVELS effect.

Adjust the blur to your liking, then adjust the GAMMA on the levels effect to choke the blur into your edge.


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John CuevasRe: How do I blur the edges of the alpha?
by on Apr 26, 2012 at 12:07:06 am

Channel blur allows you to directly blur an alpha.

Johnny Cuevas, Editor
Thinkck.com

"I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work."
---THOMAS EDISON on inventing the light bulb.


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Kevin CaminRe: How do I blur the edges of the alpha?
by on Apr 26, 2012 at 9:48:38 pm

Thanks everyone for the great suggestions!

And, yes, I got the Channel Blur to work, but it's not a straight forward process. If you blur just the alpha channel, but the R,G, & B channels are not blurred, it won't create a soft edge because RGB channels are still "hard". But if you blur all color channels and alpha, it works, but the entire image is blurry at that point and you'll need to dup the layer and do a matte choker or some other technique on a top layer.

Best regards,

Kevin Camin


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