Tracking a shot with focal variation (zoom) At the half of my shot (constantly moving camera) there is a focal length change. In my first tests the camera is moving forward instead of zooming into the scene. Is there a trick to automatically detect the focal length change?  

Is it currently possible to reconstruct the camera from such a shot at all? Until now I only have found this proposal, but I could not figure out if this is part of blender.
Sadly, this is not possible in Blender. There are other pieces of software which can do what you wan't:


Voodoo (thanks, someonewithpc)
Adobe after effects
Syntheyes
Mocha Pro
PFTrack (thanks, cgeaton)


Some of these are a little expensive, but they are all far superior to Blender's tracker in many ways.
Note: Mocha is the best matchmoving/roto/cleanup tool out their. by far. (No affiliation, promise), PFtrack also is very good at what it does, but it is still a point tracker.