OK, so I have a few questions about teleconverters first. 1. All of them claim only AF properly with aperture of f/xx or wider. So, if I used my 55-200 VR (f/4-5.6) with a 2x teleconverter (2-stop penalty), effectively making it f/8-11, would it not AF, even if the subject was bright and contrasted object in broad daylight? 2. This one's a bit more specific: do new Kenko Nikon F-mount teleconverters work with old Nikon AI lenses? 3. What do you make of teleconvers that sit on the end of a lens like a filter? Do they actually work? What is the effect on image quality? Do they give sharp results? Next question is about wide-angle converters, but along the same lines of the #3: do they actually work? How is the image quality? Are they sharp? Do they cause a lot of distortion?