I have read before that Nikon's pro lenses are usually spot on and do not require focus tuning on the higher end Nikon bodies. I include the D300 in that. I shoot with a D300 and so far I've been very pleased with the focus accuracy of my pro lenses. I'm now wondering whether I may get even better results by focus tuning. My D300 had had a recent service, and it focus calibrated, so it should work perfectly with pro lenses, surely. Can I ask how many of your pro lenses, particularly your 500mm f4, needed adjustment? I was also under the impression that focus tuning a zoom lens was a thankless task, due to the a variable focal lengths. What might be good at 70mmm, may not be as good at 200mm, and vice-versa. I would be interested to hear your opinion on this. Thanks in advance.