heeey,
I discovered this despill technique here in this forum and use it sometimes.
Right now I’m working in nuke and wanted to put this technology together in nuke.
I’m not a nuker at all and wanted to ask if anyone knows how to assemble this technique in nuke.
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I don´t know if there is an specifical node to separate channels a la “mono” node, but you can separate channels with shuffle node. Merge for Comp node and shuffle again to recombine.
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I have never used this setup, i kinda get what this is doing but keep in mind that
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nuke blend modes are not the same math
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nuke uses a linear working space so some math works different,
There are 1 billion ways to remove spill in nuke though pxf killspill comes to mind
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You can also use Nuke expression node with g>(r+b)/2?(r+b)/2:g expression in green channel.
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One correction, to get precisely what your Flame setup do you need to place
r>g?r:g
in the red channel and
b<g?g:b
and leave the green channel untouched
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I’ll try that, thank you very much!
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Ye gads look at it what it does to the skintones though. You’re in the Land of the Magenta People! I would use that only for the edges if possible…
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While expressions like this are cool, Nuke has some keyers that are excellent at spill suppression. In particularly Keylight will usually do a nice job out of the box and you can dial it in further through the UI in both color and strength.
So I would consider putting an instance of Keylight on it, sample the green, and then comp that onto the original with either an edge matte, or one of the existing matte channels. So you’re not using it as your keyer, you’re just using to it as spill suppressor.
There is also a very well regarded kill spill gizmo worth looking into (https://www.nukepedia.com/gizmos/keyer/despillmadness)
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I too am a sucker for keylight despill 
it just works really well for most things.
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I normally use Master Keyer Front CC output as a quick despill, but just tried this rig and it works very well. A little cleaner in places. For the edges only of course. Thanks Fabian!
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