Re: A step backwards
Fair shout! Thanks for the clarification.
On the subject of distinguishing background from foreground, our two eyes do this all the time stereoscopically (actually, make that most of the time, since I don't seem to be completely immune from hitting my head on low tree branches in a forest). It might be the desire to accentuate background blurring in two-dimensional images is an attempt to make up the absent information our eyes would perceive in a three-dimensional scene.
Occasionally, when scrolling through my library of photos, I will skip between two photos that were taken in quick succession but with a slight shift in camera position. This seems to cause my brain too interpret the images as more '3D', and 'pops' the people out from the background.
There have been stereoscopic cameras sold, as well as the Lytro camera which can achieve the same but by different means, but of course viewing the resulting images is often more faff than it is worth.