I have the 50-500 and a Pentax DA*300. Weather has been bad but I have taken lots of pictures of my backyard birds out of the window with both lenses. Distance is about 10ft. I am really impressed with the quality of the 50-500mm at 500mm compared to the DA. And yes, I have been able to crop DA* images to the size of the 500mm and get great results. Kind of makes me wonder why I need both. The 50-500 is more versatile for framing since it is a zoom.
I think I will probably keep both.
Last edited by GaryH; 02-04-2011 at 01:21 PM.
Reason: remove errant character