I think it's not a problem of the DOF shader. It's more a problem of the level design (maybe caused by different resolutions of the light textures/sprites?! Or maybe an additional blur shader is used for the lights number 1, and is not used for the light number 2?!).


The problem is, that the light on picture number 1 looks more blurry than the light on picture number 2.
But the light on picture number 2 is far away, and should be as blurry as the lights on picture number 3 and 4.