Long Lens Quandary - Update
After 2 weekends in a row of missing shots from the car 'cause I couldn't get my 500 in position fast enough, I became frustrated and decided that I needed to find a better way! This is supposed to fun but I just wasn't enjoying myself... And I decided that I'd be willing to sacrifice focal length for portability....
I rented a 400 DO for several days and shot some tests with it on both my 40D and 7D, and the images were on par with what I got from both the 500 and the 300 I had prior to the 500 ... very sharp, and less than 1/2 the weight of the 500! So last week, I made the plunge. Thanks to the great rapport I have with my dealer, I was able to get almost what I paid for my 500 and picked up a new 400mm f4 DO IS. I spent several hours shooting with it yesterday, and I couldn't be happier with it's performance and it's size. With the 7D, it's a killer combination and although it slows down a tad with the 1.4x, quality is still way up there.