Having solved the problem of keying silver grey hair against a green background, I am now finding that when i park up on a frame its pot luck whether or not all the edges in the image will appear really jagged (very square looking horizontal protrusions).
It looks like an Interlaced problem, but its not throughout the comp, and the footage is not interlaced anyway - it a .tga sequence. I can move around a few frames and return to the problem frame and the problem will have gone, yet if i render a sequence, its all the way through.
As I don't know what the possible causes of this are, I am having difficulty solving it. I haven't rtfm on this occasion because i have no idea what this would be called or what heading it would come under.
As ever I would be very grateful for any advice.
adam