Extremely fast and quiet focus that is spot on target. This lens is a little heavy, but you can feel the quality every time you turn the zoom ring. Usually, you have to wait until you see the final pictures to judge a lens, and this one gives you great pictures. But, what's amazing is that I can tell a huge difference on this lens, just looking through my camera. Even my friends, pro or amatuer, all say WOW! when they look through my camera for the first time with this lens on it!I love shooting with it wide open, while trusting the accurate auto-focus. I've been looking for this lens' "sweet spot", but haven't found it yet, because ALL the pictures look great, regardless of the focal length or aperature that I choose.