There is a background image. We can take a new picture with some white/black background, and select the required parts from this new photo and put it in background image. This can be done using any photo editor, say Photoshop.
But my question is, is it possible to set the custom background in camera, so that we can adjust the zoom properly to match the background image. Something similar to PhotoBooth in Mac OS X.
Is it possible to do this in an SLRs?