Any results with mirror lens, 800/500 on GH2?
MF at 1600mm equivalent is really difficult even if you can hold it steady.
I researched this a while ago and the best of that type of mirror lens seems to be the Rokinon / Samyang 500mm f6.3. It is the sharpest / highest contrast and even has decent close focus. This is a review of the lens on the Canon EOS 5DMKII: http://www.youtube.com/watch?v=L5aQjbU4Jog