Ed Sanford
I recently purchased this lens, and photographically, it is everything that it has been built up to be. The images are tack sharp, the auto focus is phenomenal, and it is great in low light. It fits in with all of the Canon L glass in their system. What I didnt research well is how monstrously heavy this thing is. I have the 100-400 II and this lens is nearly identical in weight. My take is that if I am not shooting, I can use it as dumbbell to help build the muscle that I am going to need to tote this around. It is a 5-star piece of gear. I gave it 4 to attract enough people to read this review and understand that this lens is monstrously heavy for its focal length(s). Other than that, I love the lens. I am just going to have to get in shape to be able to carry it. I do landscapes; so for the most part, it will be used on a tripod. However, it is going to be in my backpack and contribute to my leg workout routine.