It's slow, but it's never been so slow for me that I've missed a shot. You just have to be realistic about what you're using it for. I've even shot some indoor sports with it, but you have to remember that with such a shallow depth of field, you'll want to take a few more shots than you would if you're shooting at f2.8 or f4. I've shot 95%+ of my images with it at f1.2 though, so take that advice with a grain of salt. To my way of thinking, if you're using it much above f1.2, then you're not getting anything out of it you couldn't get with the faster focusing f.18 or a 70-200 2.8...