After using a Canon 300mm f/2.8 prime for sports action shots, I wanted to see what a 400mm f/2.8 prime performed like on the field. Often you get in spots that you wished you had a little more reach.
I had the chance to give the 400mm a try for a game I was trying to get a few shots that would be suitable for a magazine cover or print advertisement. I found that it was a really fast lens, of course in the sense of wide-open f2.8 light catching ability, but paired with the Canon 1D Mark V, the combination just nailed every shot I wanted because of the focusing ability of the lens and the processing power of the 1D body. Although the camera/lens combo was extremely responsive and impressive, I found that 400mm is just too long for most situations on the field. You’ll find that you’ll get a lot fewer shots, but extremely good ones. And you’ll realize that the standard zones for photos you use with a 70-200 f/2.8 are too close.
My overall opinion. Great combination, great lens – but I still think the 70-200 right on the sidelines with a fast body is the way I would go for most cases. With that big of a lens, you really need the 70-200 on another body with you anyway.