@ozzelot it's the minolta-designed 500mm AF mirror lens. in the right conditions it is amazing. in the wrong conditions it's merely a mirror lens...
(massive seperation between subject and *anything* else in shot, otherwise you get the doughnut effect, especially on lights)

@ozzelot I started on A100, used up a few (shutter buttons wear out, who'd have guessed) and now on my second A700 (shutters wear out on those before the buttons - an improvement I guess)