Can't speak to the II's, but Cookie has used a "I" for several years and it's been wonderful. Putting an extender, even a 1.4, on any lens is pretty much a waste. One always drops F-stops and a bit of crispness. One is getting a lot of lens for the money and the newer II's are really not that expensive. Step to a prime 500mm and one is getting into serious bucks. Most reviews rave about the II's quick focusing as well.

The only benefit to the telescoping "I" is one has a slightly longer platform at the high end that offers more stability for hand held shots. Cookie can easily do handheld stuff in the field at 400mm. With her prime 500mm, there's little chance of success. The 100-400 is near ideal for field sports. Courtside indoors, it may be a bit much.

Also, if one is using a crop sensor, he effectively has a 160 to 640mm unit in his hands. That's a lot of glass for the price.

If Cookie did not already have the "I", I'd most certainly spring for the "II."

A sample from her "I" on a EOS 50D. When one can count whiskers, it's pretty good glass, and this is about an 89% reduction for use in this forum.
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Last edited by 1minute; 03/08/17.
1Minute