My comments, questions and enhancements

[Peter Suetterlin]

> Another question: Can I customize the factor for focal length
> calculation? The calculated focal length is not correct for my
> camera. For a landscape image a focal length of 38,601 mm is
> calculated. The correct focal length would be 34 mm.  

Hmm, what do you call 'correct'?
I guess the important thing, the FOV, always also depends on the
distortions introduced by the lens.  As those distortions depend on
the focal length, you will need a different calibration factor for
different focal lengths....
Also, if you  optimize both lens parameters and FOV, you will most
likely get different values, depending on where you put the control
points.  

  Pit