Originally posted by Tjompen1968 I did some additional testing with the K-1 + Pentax 1.4x TC + 150-450 and the vignetting depends on how much the sensor moves to help me stabilize. It is a minor problem since when it comes to wildlife I always have to crop. If I am on a monopod and pretty stable it almost does not vignette but there is a small loss in the corners. IQ vice I have not descided yet.
Thanks for posting. I am looking forward to the Forum review - specifically tracking in AF.C since most of my wildlife here is birds and I would like to spend more time photographing birds in flight. If the K-1 provides a significant improvement in tracking over the K-3, I will probably get one even at 4 fps and a vignetting TC.