How to fix despill artifacts

- [Instructor] If the despill coming out of a keyer…is a problem,…there's no way to mask off the spill supression…inside the keyer…so the only solution is to fix the artifacts downstream.…So let's cruise in here and take a look at what we've got.…So here's our original green screen…and here, the keyer has done the spill suppression damage…on the yellow that we're worried about.…Again, I'm not picking on Keylight.…They all do it.…I'm just using this as an example.…So what I want to do is find my spill map.…

So I'll subtract the despilled image…from the original green screen…with this Merge node set for minus.…So there's my spill map.…So what I want to do is isolate the part of the spill map…that's doing the damage and then add it back in.…So we'll draw a little roto here…to isolate the region in question.…I'll use this Grade node to mask off everything…except the bad stuff that I want to add back.…Close that.…

Then we add this to our original Keylight like so.…So now you can see I put back…not quite all of it.…Just to make sure that we're dead nuts on…