odd white artifact on keylight despite having no white-ish things on the original footage

[uhm22183847l9ys]

Hi, I'm new to adobe after effects. I'm currently trying to remove green screen from my footage. The problem is, there is this white artifact on the arms despite not having any white color in the original footage. How can i fix this? I'm using adobe after effects 2020.

[Mylenium]

That happens when you overdo it with the rollback options and other stuff. Impossible to be more specific without seeing your settings. that said, the shot is so poorly lit it will be hard to do any keying. You likley have better luck just using an adjusted duplicate layer to make the guy fully blck as an inverted track matte.

Mylenium

[Joost van der Hoeven]

Those are green parts that have been desaturated. Will need som more info. What is de codec of your footage? If it is h.264 are you using the Keylight + Key Cleaner + Advanced Spill Suppressor animation preset:
https://helpx.adobe.com/after-effects/using/keying-effects.html

[uhm22183847l9ys]

Yes, the video codec of my video is h.264 and for extra information the file type is .mov. Also, I am using Keylight, Key cleaner, and Advanced Spill Supressor.

[ShiveringCactus]

Even with that amazing preset (I say amazing as I only learned of its existence recently) I think you may still need to tweak the keylight settings.  Possibly add another keylight effect before the presets, to create a solid cutout with a tiny green border (you can do this by adjusting the Screen Matte settings (clip black and clip white to make the subject solid, and then screen grow to create a small border). 

[uhm22183847l9ys]

After some tweaking, I realized the white-ish things are the "residue" of the green screen being desaturated by the advanced spill supressor. What Mylenium said was probabbly light, it is caused by a poorly lit green screen.