Background's color that was corrected showing up again in fast movements

Question

I color corrected a shot and the color of background was changed via secondaries, just like a chroma key situation.
It works very fine, except when the actor is moving faster:
For example, when he moves an arm a little faster, then it creates a king of flicker, because the old color of the background is "coming back" on the edges of the arm, during the movement.
In FCP, when I go frame by frame, the shot is fine, the arm moves frame by frame and you cannot see the previous color of the background on the edges of the arm.
I see the problem on the TV, when watching a burned DVD. I tried Compression markers on the movement but it doesn't help.
I wonder if this due to Color or FCP or Compressor.
Thanks.

Answer 1

Most of the challenges that you're encountering are common compositing woes.
Whether its film-originated shutter blur or video interlace, motion generates values in the transitional zone that can't always be solved with a single approach.
COLOR was never intended to be a compositing tool. That is why there is AfterEffects and Shake and all the rest. A roto-scoped vignette probably won't help and will be arduous at best. A major contributing reason is that you would need a shape for every field, not frame, which is all you can do.
Try a second cloned layer in Final Cut if you don't want to deal with a dedicated green-screen/compositing application. Use your original as the foreground, cut a matte with it and reveal your cloned layer which you could re-correct with the three-way FCP correction filter.
With an app like Shake, which accounts for interlace, you can generate several mattes, extract and create alpha channels, dodge them, dilate-erode-blur them, combine mattes and so on til the cows come home, have a beer and leave again. Which I believe I will do.
jPo