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Blending modes having no effect?

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Olly LawerBlending modes having no effect?
by on Sep 10, 2012 at 12:15:14 pm

Hi,

I've got white image on a black background. I'm trying to key out the background. I thought you could just use the blending mode: Add, or Multiply. But no blending mode is having any effect - at all.

I wonder if I am missing something?

I rendered the file as a MOV too and brought it back in to see if this would have any impact, but still the blending modes have no effect.

Olly Lawer


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Vishesh AroraRe: Blending modes having no effect?
by on Sep 10, 2012 at 12:33:19 pm

Mr. Lawer
You can use Add, Lighten or Screen to remove the black BG. If its not working, then pre-compose your footage and change blending mode.

Also, you can use " Luma Key " effect to remove black or white from your footage.
Go to Effects>Keying>Luma Keying

Under effects panel, twirl down Luma key and choose "key out darker" in "Key type".

Now increase the Threshold. This will remove the black from footage.

If you will choose "Key out Brighter", it will key out white.

Vishesh Arora
VFX and Motion Graphics Artist

http://digieffects.wordpress.com


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Vishesh AroraRe: Blending modes having no effect?
by on Sep 10, 2012 at 12:35:54 pm

Also you can use "Red Giants Knoll - Unmult" plugin which is free to download. It will key out black with just one click.
Here is the link: Its a free plugin

http://www.redgiantsoftware.com/blog/2010/08/17/knoll-unmult-free/

Vishesh Arora
VFX and Motion Graphics Artist

http://digieffects.wordpress.com


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Mato KokoticRe: Blending modes having no effect?
by on Sep 10, 2012 at 4:21:46 pm

You CAN NOT use Add, Lighten or Screen to generate Alpha and render with Alpha. All blending modes needs underlying layer.
Luma Key and Unmult, however, are different story :)



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Vishesh AroraRe: Blending modes having no effect?
by on Sep 11, 2012 at 7:30:41 am

Mr. Kokotic
I know we can not use Blending modes to generate alpha.
But the question is to remove Black bg and this technique works fine in that case.

Vishesh Arora
VFX and Motion Graphics Artist

http://digieffects.wordpress.com


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Darby EdelenRe: Blending modes having no effect?
by on Sep 11, 2012 at 9:55:59 am

In most cases Blending Modes are the wrong way to remove a black background. It would be appropriate to use a blend mode like Add or Screen if you wanted to blend the layer with a background but otherwise trying to use blend modes for this purpose can lead to greater confusion or incorrect results.

Your other suggestions are good and I'll add the Extract effect to the list.

Darby Edelen


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Dave LaRondeRe: Blending modes having no effect?
by on Sep 10, 2012 at 10:53:04 pm

I think you might be confusing a blend mode for a track matte. A blend mode affects the pixels of underlying layers in various ways. A track matte is used to create transparency.

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


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Olly LawerRe: Blending modes having no effect?
by on Sep 11, 2012 at 8:29:11 am

Thanks for this.

I watched a tutorial once where they brought in some footage with a black background and simply applied ADD from the blend mode and as if by magic it keyed out the background. Never been able to replicate since.

Luma Key worked a treat. Thanks

Olly Lawer


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