Wouter The reason the 500mm comparison is valid, for me, is that I cannot afford a current production AF 500mm lens; neither the $1,400, 200-500 f/5.6 zoom, or even worse, the $10,000, 500 f/4. Especially not for a lens that would be used so infrequently. I admit that manually focusing (focus tracking) the 500mm mirror on an actively moving subject, like the tennis player I was trying to shoot, was VERY difficult, with a LOW hit rate. I think my focus hit rate was about 10%. So I had to shoot a lot, to get a few keepers. Shooting active sports is a place where AF really shows its value. But for non-moving or very slow moving subjects, the manual lens does just fine. Lack of VR, yes, a problem that gets worse the longer the lens. I shoot the 500 off a rest or a gimbal+tripod. Hand held, I need to work on my hand holding technique for that lens, and I will have to shoot at 1/1,000 sec. No illusions, I know how hard it will be to hand hold that lens. So for me, the old manual mirror lens is a "good enough" compromise for the general tasks I have, at an affordable price.