This is the uncropped content of a picture shot at 135mm through my sliding door. I am approximately 12 feet from the squirrel. After nice results from my 90mm macro perhaps 6 feet from a squirrel, I decided to see how close I would get with a 135mm setting on my 100-400 lens, which when zoomed to 135mm shuts down to f/5. How nice it would be to have the 135mm f/2 lens for this kind of shooting. With its legendary sharpness a crop like the next one wouldn't suffer very much, huh?