Out of the many things I'v seen on these boards, one of the most amazing has probably been the clips where people have completely removed an element (in these two instances) an actor from the scene.

The two clips I'm thinking of are the following;

Superman II - Removing 'Duane' the Policeman as Zod and co exit a cafe (just before the English kids dad is lofted up in the air

Superman III - Completely removing Gus Gorman when supes is at the coal mine.

Now, if these were filmed with the exact same camera movements over a blank plate and identical lighting I would know how to do this but on earth do people accomplish things like this? How is a person deleted and for it to look flawless underneath?

This for me is one of the big mysteries of video editing and whilst I feel I have the software, I don't have the nowhow and would love to find out!