Chroma Key Noise Issues.

[Brendan Coots]

This is a common problem that has many, many possible causes. Here’s some usual suspects and possible solutions:

– poor lighting on the green screen, resulting in the keyer having a hard time with fine details like hair
– Reshoot, or sacrifice the hair detail in return for a more smooth effect

– poor keyer settings that are pushing and pulling the footage in two directions at once
– Start over with fresh key settings, and do things one step at a time to ensure you aren’t overcorrecting. Set the key color, adjust the matte values and go from there.

– blonde hair picking up a lot of green screen spill, making it tough to key
– Reshoot or key agressively to remove the hair in return for a smooth key

– noise introduced by the keyer
– This doesn’t really sound like it applies to your situation. The solution requires multiple steps so I’ll skip it for now

– trying to use a “catch-all” keyer setting for the entire subject
– Divide up your keying according to needs. If the head has fine details it might warrant its own keyer settings, as will other trouble spots. Duplicate your footage once for each “problem spot” identified. Using masks on each layer, isolate the elements so that each layer represents one part, such as layer 1 being the head, layer two the body and layer three some other problem area. Now key each layer with its own settings, optimized for that particular task (such as the fine hair on the subject’s head). This is how the pros routinely key on feature films, even with perfectly lit film plates.

Brendan Coots
Splitvision Digital
http://www.splitvisiondigital.com