"Jake Hellbach" <[EMAIL PROTECTED]> writes Hello, Has anyone used the Sigma 135-400 or the 170-500 lenses? Sharpness? Problems with autofocus ? Also the Tamron 200-400. Not the Sigmas but I have the Tamron in question. It focuses very well with my F90X. Others have criticised it for being softer than the fixed F.L. alternatives, i.e., Sigma and Tokina. Can't say as I have not compared them. It seems pretty good to me even at 400mm and wide open. My site has a shot taken with it. See following URL if you are interested. The shot in question is the chickadee photo on this particular page. Sorry but I don't recall if it was at f/5.6 or f8.0 though. http://www3.ns.sympatico.ca/danksta/small.htm Incidentally, I had a complaint about my "vcard" in previous posts taking up too much room. My apologies. I was just trying to attach a sig file and didn't even know what the v card thingie was. Turned off now (I hope.) Terence A. Danks Nova Scotia, Canada http://www3.ns.sympatico.ca/danksta/home.htm