reverse motion blur

The only way I can see that being done is to greenscreen the moving object and superimpose it on a blurred background.

Okay - here's the concept (you can execute it in either Motion or FCP).

You need to create a "difference" map. The easiest way to do this would be to take your clip and layer it with either a freeze frame of the clip, or the same clip offset by some number of frames. You put the original clip on V1, your freeze frame or offset clip on V2. Set the composite/blend mode to "Difference". This makes everything that's the same black and what's different white.

You can then use a Compound Blur filter and feed it the difference map. Compound blur blurs more in lighter areas and less in darker ones. You'll want to invert this. This will cause everything that is the same to be blurry and things that are moving to be clear...

make sense?

Patrick

Sounds OK to me.

Years ago I tried to make a difference map for something else (which I can't remember!), but it didn't work.

So I will experiment with your instructions and see if the memory returns!