canon telephoto
i have a 600mm lens(non IS) on a tripod for my wife to take photos of the osprey and the babies down their nest. the canon 6D will auto focus, she has shot a couple thousand images over the past 3 years. and we get quite decent photos. i bought a 1.4x IS extender for her. works great. i bought a 2.0x extender, and the camera will not autofocus. (all canon equipment) need help.