Can anyone tell me how to render a scene in maya with a see through background so that i can just put that scene over any picture or movie clip i want?

The black background always comes up, i could photoshop every frame but thats a lot of work ;b , so if there is way to render it already see through i d really appreciate it =)

I hope my question is clear enough =S
I m using maya 8.5


Thanks:attn: