In Photoshop (current version is CC 2014 (2014.2.1 20141014.r.257 x64)) I did the following steps of interest:
- duplicate background w/subject masked
- apply a blur filter of some kind to the background, heavily.
Now since the subject was carefully masked (thanks to Select Focused for doing most of the work!) I have an effect that looks like a very shallow depth of field. The uninteresting background can be abstracted.
However, I get an unwanted border around the subject. The blur of the background includes the subject which spreads out to affect the color of neighboring pixels, and that shows up as a fringe when I drop the sharp version of the subject in.
I tried adding an inverse of the mask to the filter layer's mask, but it didn't do anything.
Is there an easy way to address this? I'm pretty sure that the overall approach is the classic way of doing this, so I must be missing something.
(I used the Blur Gallery, with Field Blur or Iris Blur. It doesn't matter since the mask generated is applied after blurring the entire image)