Jim;

I think you would really love the 400mm f5.6; it is a super sharp lens and a really fun lens. Great for candid shots at the dog park, it is light and very easy to hand-hold, and it will open another arena for you in photography-a bit of wildlife photography. It is awesome at at the beach shooting pelicans, gulls, etc. If you could swing it, I think this could be an awesome purchase. I only wish Nikon made something like it, once I switched to Nikon, I really miss that lens.