Paul, that lens doesn't allow for too much sudden anthing. It's a behemoth of a manual focus lens. It's very sharp but it requires careful focusing. I use mine often with a small extension tube to shoot birds through a window. The bird pretty much fills the frame at 6 feet.
If you need to be quick then the 600mm autofocus is a better lens (if you can afford it). I love my 500mm 4.5 for what it is. A damn good optic that does what I expect it to do at a great price. Paul Franklin Stregevsky wrote: > What is it's closest focusing distance? > 10 meters. Tom Reese wrote: Add a small extension tube and you can get a lot closer than that and you get the Pentax optical quality. You do play a price with reduced light. I dunno about you, Tom, but an extension tube on a telephoto designed for such a long reach might require a quick-change artist. Imagine you're focused on a bird 50 meters away. Suddenly a rabbit appears 6 meters away. Do you tell the rabbit, "Hold that pose while I install my close-focus tube?" You can't keep the tube in place at all times, or you'll lose the distant focus.
