shadow cather dosent work appropreiated with footage as background I create some mesh as 'shadow cather' so that I could 'cover' the area I don't want to show up.
When I render it without background it seems works fine.
But it doesn’t works with a footage/image as background.
(you still can see it through!)

Anyone knows why?
I can't guess method you used but the preferred way to compose render result with background is to use Alpha Over node