I'm working on a scene that has a character lit from behind and has a long shadow cast in front of him. I want to create a gradual blur so that the shadow is crisp around his feet but obviously gets more blurred the further away it gets.
Isolate the shadow in whatever way you fancy. Create a solid with a greyscale gradient that matches the angle of your shadow. Apply Compound Blur to the shadow, referencing the greyscale map. Alternately use Lensblur to the same effect or third-party products such as RevisionFX' SmoothKit. If the character is in front of a bluescreen/greenscreen, don't bother with the shadow at all, just use the extracted character and derive a shadow eitehr using manual techniques on duplicates (3D layer, Corner Pin) or with Red Giant Warp's Shadow.
Brilliant, thanks again. You helped me with my previous question too!