When the walls of reality thin, and Others start squirming through, will you take a stand or be a crunchy snack?
I really like this environment, but I was disappointed that I couldn't use camera DoF as the background was all the same distance (obvious when I thought about it).
However, I remembered a flaw in the way the renderer handles DoF - the blur amount is taken from the first reflective or refractive surface hit.
So I added a geometry shell to the shadow catcher and gave it a push distance of -0.2 to get it slightly behind. Set diffuse, specular and opacity to 0. Set refraction to white and 100%, IoR to 1.
And joy of joys, it worked - the background is blurred to the right amount for the view. I even used this to bring the close tree forward a bit with a scaled plane aligned over the image at the right distance back - not perfect but sort of works.
Anyway, hope this method helps someone else who wants to use DoF with this.
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