All replies really worked! I am completely new to keying and compositing(I’m a Mental Ray guy)and the first reply really came to be very useful indeed.
thanks!
and I also have many footages of Hollywood Camera Work.
your solution got to work, but it continues to have a transparent green bg instead of a full transparent bg.
I’m using Primatte Keyer plugin.
In fact with key light plugin I go completely O.K with no cutting-in error and everything looks fine.