There are loads of camera apps for iPhone, broadly offering the same kind of pro-level controls: manual focus and ISO; white balance; zoom; levels; filters; grids. Obscura Camera is in this respect more of the same, but what makes it worthy of consideration is its really smart interface.
Next to the shutter are big ‘expose’ and ‘focus’ buttons, for locking each feature. Above, chunky ISO and shutter buttons beg to be tapped, and can be quickly swapped out for a raft of other controls. Want a different filter? Just swipe across the main viewfinder area.