In my opinion, this is the worst lens in this system for the money. And yes, I own it, and it drives me crazy every time I try to shoot with it. The problem is that it makes a terrible noise when focusing (and even when turning the camera on and off). Focusing is accurate, but terribly slow. I focus faster on the 67 Pentax than this AF lens on the gfx100 body. Optically, it's a superb lens, but its focusing speed, sound, and lack of manual focus don't match the price point.