Multiple camera in iphone project expensive?

Howdy all, and thanks for your attention.

I am doing a top down camera (non-orthographic to get some parallax scroll) 2d game and am using multiple cameras as children of a parent cam to render different objects in layers in the scenes to stop the object from tearing and sorting through each other. Is this an expensive thing to do?



I've got several cameras in my iphone game as well as a load of physics and particle effects and it runs fine, go nuts.