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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.

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Sadly, this is not possible in Blender. There are other pieces of software which can do what you wan't:

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.

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    $\begingroup$ add also PFMatchit and PFTrack Both are capable of tracking shots with variable focal length. $\endgroup$
    – user1853
    Nov 20, 2014 at 2:40
  • $\begingroup$ @cegaton I was looking for PFTrack but failed to find it. It costs as much as a (well) used car though. But the object tracking is to DIE for $\endgroup$
    – GiantCowFilms
    Nov 20, 2014 at 5:48
  • $\begingroup$ @GiantCowFilms - Thanks! How do you know that? Just your experience? Can you add a reference, paper or wiki-link why this is not possible in blender? $\endgroup$
    – p2or
    Nov 20, 2014 at 11:19
  • $\begingroup$ @cegaton - Thanks! If blender really fails to solve this shot and especially in terms of reconstructing the camera, pftrack is one of the best options for sure. $\endgroup$
    – p2or
    Nov 20, 2014 at 11:27
  • $\begingroup$ @poor I know experts (who have worked on open movies) and such who have tried and failed to do what your asking. $\endgroup$
    – GiantCowFilms
    Nov 20, 2014 at 15:24
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the gsoc 2013 proposal you linked to doesn't seem to be included in blender master/trunk yet, so you won't find it's features in the latest version.

You can use a special build from the GsoC 2013 motion track branch though. http://graphicall.org/1063

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  • $\begingroup$ Thanks guest! I've tested the build, sadly with no success. There is a new "constrain focal length" checkbox as part of the refine settings. With this you can enter a min and max value of focal length, but when I setup my values it has no effect and the camera is still moving forward like in the current build. $\endgroup$
    – p2or
    Nov 18, 2014 at 16:46

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