I'm considering Tamron 200-400mm along with F80. Should I go for this lens or the Sigma 170-500mm or the Sigma 135-400mm?
I have seen considerable vignetting with the 170-500 at 500mm end, but have not seen the results with other two lenses. Does the constant aperture lens (200-400) have any advantage over other two?How are the results of 200-400mm with a 1.4x Teleconverter?
Your valuable comments please.