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Using Keylight for Luma Key? Luma Key effect "obsolete"?

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Scott Clements
Using Keylight for Luma Key? Luma Key effect "obsolete"?
on Feb 20, 2015 at 12:46:14 am

Hi,

I am trying to luma key a human hand against black in After Effects. I initially tried using the luma key in Premiere and it worked great, but I was unable to add a mask. I am new to Premiere, so may be doing something wrong, but I just couldn't implement a proper mask - the way I can in After Effects.

So, I went to After Effects and tried to make a luma key using the luma key effect. No dice. No matter how I manipulated the key, it looked absolutely terrible - super crunchy - almost as though the footage was sot on DV or something - not what I expected at all.

So, I found out that After Effects says the luma key effect is "obsolete" and suggests using the keylight effect instead. However, I've never known Keylight to be able to pull luma keys. I googled up on it and other people said the same thing.

So, why is Adobe telling us to use keylight for luma keys? How do you pull a luma key in keylight? Any other methods?

Film Editor, London UK
http://www.scottclementseditor.com


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Steve Bentley
Re: Using Keylight for Luma Key? Luma Key effect "obsolete"?
on Feb 20, 2015 at 1:15:47 am

Instead of fighting with Luma key (especially with something shot on black) we'll often just take a copy of the footage and crush it with a Levels filter and then either use a slight blur or use the matte choker to smooth it out a little. At least this way you can move the edge of the matte in and out and add as much anti aliasing to the edge as you like.
Then take the original footage and use a luma track matte to pass it through this hi contrast "window".



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Steve Bentley
Re: Using Keylight for Luma Key? Luma Key effect "obsolete"?
on Feb 20, 2015 at 1:54:48 am

Forgot a step - make sure to apply a HSL filter and desaturate totally before running the levels filter on your matting elements.

Good thought Dave - didn't think of that myself - you can also use the matte choker with the extract filter to finesse the results.

Another trick we will do is to "bipack" the original or some desaturated version of it. Just do a precomp with two copies of the original "multiplied" on top of each other. This will magnify the density of the non white areas. Then, in the outer comp pull your matte with any of the above suggestions. This of course depends on how white your white is.
Dont hesitate to run a degrain or denoise before any of this. Yes it softens it but that's not always a bad thing where mattes are concerned. But mostly is smooths things out before you start to crush the levels.



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Dave LaRonde
Re: Using Keylight for Luma Key? Luma Key effect "obsolete"?
on Feb 20, 2015 at 1:29:30 am

You could try the Extract effect. That works pretty well.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Walter Soyka
Re: Using Keylight for Luma Key? Luma Key effect "obsolete"?
on Feb 20, 2015 at 1:54:17 am

[Dave LaRonde] "You could try the Extract effect. That works pretty well."

This.

Luma Key is considered obsolete because Extract does everything Luma Key did, and more.

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


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Matthew Wood
Re: Using Keylight for Luma Key? Luma Key effect "obsolete"?
on Feb 20, 2015 at 8:10:55 am

Well, so this is, generally, true, but not entirely. Luma still has options not available in extract

-----------------------------------------------
Blood type O negative. I bleed zeros and ones

I dabble on the desktop

Shifted Leering, Any Perspective
Shifting Literally All Perceptions
SLAP


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Scott Clements
Re: Using Keylight for Luma Key? Luma Key effect "obsolete"?
on Feb 20, 2015 at 12:00:38 pm

Thanks for all the information, guys!

Film Editor, London UK
http://www.scottclementseditor.com


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Dave LaRonde
Re: Using Keylight for Luma Key? Luma Key effect "obsolete"?
on Feb 21, 2015 at 12:29:44 am

Maybe you can tweak more things in Luma Key, but since I found Extract, I haven't looked back.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Matthew Wood
Re: Using Keylight for Luma Key? Luma Key effect "obsolete"?
on Feb 22, 2015 at 1:30:15 pm

While maybe "very" uncommon, there are still times that can be handled better with Luma key, than extract. Without the need of adding another effect, that is.

A black and white matte render that needs the alpha edges adjusted, is one.

-----------------------------------------------
Blood type O negative. I bleed zeros and ones

I dabble on the desktop

Shifted Leering, Any Perspective
Shifting Literally All Perceptions
SLAP


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Steve Bentley
Re: Using Keylight for Luma Key? Luma Key effect "obsolete"?
on Feb 24, 2015 at 12:46:20 am

Luma is still available in "obsolete" section of the effects list



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