sony 70-400 vs tamron 200-500

I don't think tests like this will tell you anything except your testing mechanics are faulty. I can take two shots in a row with the same lens and get results that are different. Both are great lenses and both take incredibly sharp photos. I personally prefer the 200-500 since it has 100 mm more reach, it is lighter, it costs less and it has less zoom magnification (2.5x for the Tammy and 6x for the Sony). I would stop worrying about testing them and just go use whichever one you like the best.

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My photos:
picasaweb.google.com/seilerbird