I updated the distortion model to the more elaborate ptlens model. This gives an even better result: <lens> <maker>Tamron</maker> <model>Tamron SP 35mm f/1.8 Di VC USD F012</model> <mount>Canon EF</mount> <mount>Nikon F AF</mount> <mount>Sony Alpha</mount> <cropfactor>1.0</cropfactor> <calibration> <distortion model="ptlens" focal="35" a="0.0032" b="-0.01061" c="0.00557" /> </calibration> </lens>
Tamron SP 35mm f/1.8 Di VC USD F012