Keep in mind that on your D7100 it is the equivalent of a 105-450mm. If you can afford a few more bucks, the Sigma 100-400mm is a good choice, and for more money still, the Tamron 100-400mm offers better weather-sealing than the Sigma with similar performance. Those will give you the equivalent of 150-600mm on your D7100.
I guess nobody understands what I'm talking about. If you want a 600mm, buy one. Don't buy a 400 mm, it'll look like a 600mm on some cameras but it's still a 400mm; glass is glass. PERIOD!!!! And looks can be deceiving!
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