How to get green spill off skin and hair

A green screen is a giant green bounce card, and it does not care that you only wanted it behind the subject. It throws green onto jawlines, shoulders, white shirts, and anything glossy. You can pull a technically perfect matte and still have a composite that screams green screen, because your subject is lit like they are standing in a forest.

Spill and the matte are different problems. The matte decides which pixels belong to the subject. Spill is wrong color inside pixels that were never in question.

What despill actually does

A despill compares the green channel against the other two and suppresses green wherever it dominates in a way the subject’s own color cannot explain. Done well, skin goes back to skin and the white shirt goes back to white. Done aggressively, everything drifts magenta, greens in the subject’s actual wardrobe die, and skin picks up a grey, de-saturated look that is its own kind of tell.

That is the whole game with spill: the cure overshoots as easily as the disease. Which is why the real question is not how to despill but where in the pipeline to do it.

Where to fix it, best-first

On set. Free and permanent. More distance between subject and screen, a magenta-tinted edge light to cancel the green, and flags to cut the bounce. If the shoot already happened, keep reading.

In your comp. If you composite in Nuke, Fusion, or After Effects, you have precise despill control there, and doing it in context against the final background is the most accurate place to judge it. The cost is time and one more node tree per shot.

Baked into the key. Key Studio Pro despills as part of the pull, tuned to whichever screen color the shot has, green or blue. For most shots headed to an edit rather than a comp suite, this is the practical answer: the Processed pass or a ProRes 4444 export lands in the timeline already clean.

Deciding between the last two

1. If the shot ends its life in an NLE timeline, bake the despill in. Nobody downstream will do it for you.
2. If a compositor owns the shot, deliver the straight FG and Matte passes and let the despill happen in the comp, where the final background is visible.
3. If you are unsure, pull both. The passes are cheap and the queue does not mind.

What despill cannot know

Despill removes green. It does not know what light should have been there instead. A subject heavily wrapped in bounce loses that light when the green goes, and can end up looking flat on the shadow side. The fix is a gentle warm grade on the affected side in the comp, which is a creative call no automatic tool should make for you.

Genuinely green subjects are the other trap. A green costume or prop sits exactly where the suppressor looks. If the wardrobe is green and the shoot has not happened yet, that is your sign to hang the blue screen instead.

Common questions

Why does skin look grey after despilling?

The suppressor pulled green out of skin tones that legitimately contain some. Ease the strength back, or restore warmth with a grade. Grey skin is over-suppression, not spill.

Does spill affect the matte too?

With a chroma keyer, badly: spilled edge pixels sit closer to the screen color and start dissolving. A neural key separates the two jobs, so spill on the subject does not eat the alpha. The edge side of that story is in the hair guide.

Blue screen spill too?

Same physics, blue bounce instead of green, and it tends to read as cold rather than sickly. The despill targets the screen color the shot actually has.

My screen itself was patchy. Related?

Different problem, same shoot. See keying a badly lit green screen.