Quote Originally Posted by EPT1955
I would truly like to purchase the EF 100-400mm L IS USM, but the reviews were not fantastic when they used the EF 70-200mm L IS II USM as the baseline. Perhaps I am placing too much emphasis on the reviews, do you have any experiences to impart?

I have and use both with my 7D. The 70-200mm is sharper, focuses faster, and has a wider maximum aperture. It's the sharpest, best quality zoom lens that Canon makes. It's also several hundred $ more expensive. The 100-400mm has a broader zoom range (4x vs. <3x), and is double the focal length at the wide end. Although the 100-400mm is slower focusing, it does fine for me locking onto and shooting birds in flight. If you only need to go to 200mm, get the 70-200. The 70-200mm + 1.4x extender is still a little better on image quality than the 100-400mm, but only gets you to 280mm. The 70-200mm + 2x extender is worse than the 100-400mm. If you need the 300-400mm range, get the 100-400mm.


Quote Originally Posted by EPT1955
Using an ISO of 1600 or 3200 with the 100-400mm might provide solid results, but I am not sure.

ISO 1600 is tolerable on the 7D. I'd stay away from ISO 3200. Keep it under ISO 800 if you can.


Quote Originally Posted by EPT1955
The reviewer mentions a pincushion effect and I have a hard time getting my arms around this concept. I am not sure how this issue would impact my photography efforts.

It wouldn't, unless you're in the habit of shooting graph paper or buildings with orthogonal grids of windows. In real life, you will notice barrel distortion (common at the wide end of wide angle zooms), but almost never notice pincushion distortion.