A few posters make a good point: Why not just get the 500 or 600?
Well, sometimes you miss shots with a prime. A good example would be a bird flying right at you. Bears with cubs are another reason why a zoom would be superior. Also, the built-in TC offers a big advantage. Changing a TC in the rain or snow is awful.
I like the "look" that primes give for wildlife. But if this lens can be as sharp as the 300 or 500, while offering the ability to pull back to 200mm to get those hooves or cubs in the frame, then it's going to be a popular lens. If it's not as sharp as the primes, then it's in serious trouble.
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