Borrowing a ef 500 F4 is mki for the week. Example shots of the difference between F4 and f7.1(to mimic my 100-500). F4 really blows out a lot more of the background and lower that iso a ton Unfortunately the lens has seen better days. Definitely less sharp than my 100-500 and the AF and stabilization are not nearly as good. I can actually get better lowlight shots with 100-500 because I can shoot at much slower shutter speeds Still find to use for the week though! photographers of threads