Keylight on green causes white artifacts

[Travis Dao]

There are three shades of green behind him and the video is about an hour long. I don’t really want to animate masks or rotoscope for the full hour. I thought I could key out each shade of green and use that as luma matte but he ends up greenish.

Thanks for the advice,
TD

[Darby Edelen]

[Travis Dao] ” My current work-around is to adjust the key so there are no white artifacts (but i lose some of his face) then do a separate key on his head and mask that over.”

Sounds workable.

Another suggestion is to consider the keying process as it’s own discrete process the only purpose of which is to get a good alpha. It doesn’t matter if the guy looks purple, orange or yellow at the end of that process. You can always go back to the original RGB, clean up the spill and matte it with the keyed alpha.

Darby Edelen

[Travis Dao]

This sounds like a good suggestion. To clean up the spill do you mean to use spill suppressor? I played around with screen gain/balance in Keylight and got some decent results.

Thanks,
TD

[Travis Dao]

I think the shot was well lit and the distance between subject and background was adequate. The three shades of green is the main problem. It was recorded in DVCPro HD is that a good codec for keying?

Thanks,
TD

[Darby Edelen]

[Travis Dao] “To clean up the spill do you mean to use spill suppressor?”

I find AE’s spill suppressor very limiting.

Here’s a sure fire way to get rid of spill. Duplicate the keyed footage, remove any other effects so you have the source, add Channel Mixer and set the Green channel to a 50/50 split of Red and Blue. Now put this layer above the keyed footage and set it to the Darken blend mode. You’ll also need to clip the layer to the keyed footage either by using a track matte, set matte or preserve transparency.

Here’s an image that shows a simple set up.

Darby Edelen

[Travis Dao]

That is a very cool trick. Thanks!

TD