Miniature blur effect

Hi !
I'm trying to find a way to reproduce a miniature effect with an isometric view : a gradient blur to any object not in the focus. I try to tweak some values with post processing effect but it ended all blurry or not blurry at all.
This the kind of result that i would like :


Any idea of the best way to did it ?

 

It's called "Tilt-shift" or "Tilt-shift blur". You can start with a legacy image effect described here
https://docs.unity3d.com/550/Documentation/Manual/script-TiltShiftHdr.html

 

Awesome ! Thanks !