DPxM: Selective focusing
With the DPxM cameras, selective focusing by pressing the focus points button is really simple and easy. Nothing complicated here.
Here's another method that may have been covered by earlier posts. Kick Tuck describes it in his review of the Sony Nex-7 at Visual Science Lab. Adapted to the DPxM camera:
Half press the shutter button to AF and then hit the focus mode button to toggle into manual focus. Now your focus (and exposure) is locked where you wanted it. Need to focus again? Hit the button again to toggle back to AF.