12, 45, 75, ???

What's the true, tested, performance of the Tokina 300mm f/6.3?  It's been a long time since I actually ran the tests, but my Tokina 500mm f/8 actually performs at around T/10.

Your suggestions seem pretty close to the mark.

Questions: how wide can I go withOUT going fisheye?, and...are there any reliable test reports on the Toking 300mm f/6.3?

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-Kenneth Sloan