I have now added a tutorial for this technique here: creativeobscura.blogspot.
If you are interested in the technique I would appreciate any feedback you have to help me make this tutorial more user friendly for everyone, thanks :).
I have been playing around with miniaturising one of Jos' photos (see here) that he took in Amsterdam on a Mamiya C330 recently. The shallow depth of field is faked using a hand painted depth mask & Photoshop's 'Lens Blur' plugin.
Although this looks similar to a tilt-shift effect it's a bit different. I only recently realised that tilt-shift lenses do not reduce depth of field, they only appear to do so based on the simplicity of the scene and angle of the view. What they do is blur the top and bottom of the image, there is nothing more to it than that (they don't increase the out of focus effect based on distance in any way). This image however is using distance (depth) information to add blur in post. There is no way to do this optically, not that I know of).
There are limitations to the technique however, foreground blur when it sits on top of the focus plane is a real pain. Also it is difficult and time consuming work to create the selection masks. All that said it can be rewarding when it works. I will post the depth mask used to create this in the comments to illustrate my point about the comparisons to the tilt-shift effect.
Hopefully my next post will be from my own Mamiya C330! I am sending the films off for developing tomorrow... fingers crossed! I am using Peak-Imaging, they sound good!