Sometimes it helps to get a view of how some other things work. I own a Canon 100-400 mm IS L-series zoom. It has an f-stop range of 4.5-5.6. I decided to rent a Canon 70-200mm IS Zoom from BorrowLenses.com and play around with how it handled some of the bird and nature photography I do.
First, BorrowLenses.com is a pretty cool setup. I was able to reserve a lens from them for a fairly good price. I picked up the lens at their storefront in San Carlos, and it was in great shape. They provide insurance for the lens for 14 dollars which covers everything except loss, theft, or water damage.
First up was to take the lens to one of my normal wandering grounds and see how it does with some of the birds there. The focusing capability with the Canon 7D was very good. I had the camera on sub-spot focusing with the center spot.
Then came trying the camera and lens out in Southern California, where I went on a vacation. We went on a walk around the Shipley Nature Center. We had been around this park before, though at that time the pond was not over-flowing like it was now. We were able to see some animals, rabbits, hummingbirds, and lots of small children.
The Hummingbird to the left was taken with the center sup-spot focus, and the lens did very well with tracking the hummer, even with the Canon 1.4 teleconverter on it. Because of the low light, I had to shoot at ISO 3200, but still it was very good.
One of the reasons for the great auto-focus ability is the f 2.8 aperture (or 4 in this case) which allows the camera to have more light than the 100-400 mm lens. More light means that there is more that the camera can use to determine focus.
Rather than try and hoist the camera around, I was using a BushHawk Rifle Mount. This allows me to steady the camera and lens much more easily than just holding the camera alone.
Finally, I went to Milagra Ridge to see what was there to take photos of. The ridge was the location of gun battery to protect the San Francisco area.
On the day we went, it was cold, windy, and foggy. We didn't see a lot until we spotted this young hawk looking for food. The wind was strong enough to allow him to hover with no problems. The photo shows him descending down trying to pick up some dinner. He wasn't successful. What was nice for us is that he came to us. We saw him fairly far away, and we were upwind of him. He came closer and closer without us having to move much, and was not phased in anyway to have us there.
While I won't be replacing my 100-400 lens, it is just the perfect range for what I do, I do recommend the 70-200 II lens. It would be a great lens to pair with a more up-to-date 1.4 teleconverter than the one I have, and would pair well with any of the Canon cameras.
All of the photos can be seen at PlayTime on my photo site. Most of them are just slightly cropped with little post-processing.