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Keying Out Large Amounts of Spill

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Max JacksonKeying Out Large Amounts of Spill
by on Jan 7, 2011 at 8:49:53 am

Hi CC,

I've been banging my head against this keying exercise for weeks time and time again. I'm trying to key out the green, but the spill runs all over my subject.

The exercise is from the Hollywood Camera Work site:

I'm swapping out key after key and using a spill suppressor and can't figure out what it is I'm supposed to do. My goal is to get through all off them, but I can't even seem to get past the basic MatchMovie Test Close exercise.

I'm bouncing back-and-forth between chewy and messy. I'd do the standard process of get a good edge first and then mask out the middle but the key spills to the edges. I'm stuck in this push-pull merry-go-round.

Is there a standard approach to major spill on a subject with hair?

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Dave LaRondeRe: Keying Out Large Amounts of Spill
by on Jan 7, 2011 at 4:40:05 pm

What kind of keyer are you using?

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

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Max JacksonRe: Keying Out Large Amounts of Spill
by on Jan 7, 2011 at 8:12:19 pm

I seem to get the closest with Keylight and the Color Difference key.

However, when I tighten either her hair gets chewy. I use a spill suppressor, but then I still have this like...thin purple (green opposite) outline that I can't shake.

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Kevin CampRe: Keying Out Large Amounts of Spill
by on Jan 7, 2011 at 4:45:45 pm

if you're not using keylight in ae, i would suggest trying it. it's a good 3rd party keyer that's included with ae (though not in the trial version).

you can download the user guide from and they have some other training resources too. they do outline a procedure that uses 2 instances of keylight to create a procedural matte (the 1st acting like a core matte, the 2nd handling the edges and spill). they also have some tips on using the spill bias and other features in the plugin.

also, aharon rabinowitz has a good tutorial on creating 'super tight junk mattes' that i still use. it creates an tight outside matte. that combined with the core/inside mask technique from the foundry can usually handle any key.

Kevin Camp
Senior Designer

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Max JacksonRe: Keying Out Large Amounts of Spill
by on Jan 7, 2011 at 8:18:59 pm

Yeah, I'm primarily starting out my process with Keylight. I'll have to check out their user guide. I have Mark Christiansen's book on the matter, but for color spill he says just fool around with the edge color correction tool. I do and it doesn't affect a single transparent pixel.

I've also played with Aharon's inverted choke and trace method. Way cool, but his animation example doesn't have any hair of feathering so I figured a lose hand-made garbage matte would probably work better. Maybe I'm wrong?

Thanks Kevin.

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Max JacksonRe: Keying Out Large Amounts of Spill
by on Jan 7, 2011 at 9:58:00 pm

I think I figured out something for now, at least it's pretty darn good for a beginner.

If another beginner is reading this, my issue was dealing with edge and spill in subject with hair blowing in the wind and spill covering roughly 50% of the matte area.

I used a two layer key, edges(top) and core(bottom).

edges: I used Keylight changing the despill bias color to facial tones to assist the core and overall spill, then pulled up the clip white until I was happy with the outline (nevermind the BG). Then I used the Color Key to select the floating leftover green screen BG grey matter still showing up in Keylight's status window. I repeated this until Keylight's status view looked clean of floating pixels around the edges. I can add a garbage matte for the rest.

core: the body of the subject was a white coat so it was picking up a ton of green. For this I used Keylight again focusing only on the body. I repeated the same Keylight method as in the edges layer, but this time selected the non-greenest part of the coat I could eyedrop for despill bias. I then used simple choker to cut down on the doubled edge. The hair is still chunky as there are two layers of it, so I'll probably just garbage matte roto out her head on this layer so her hair's not so thick at the roots.

This is from what I understand somewhat of a backwards way of doing things as the garbage matte is supposed to come first. However, I've learned that getting a good edge is the key (har har) so I started there first and worked my way back.

Thanks everybody for your input!

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