Ran into some friends of ours with their two West Highland Terriers. Decided to go to the dog park with them and tried out some action shots with the 12-40. Had the darnedest time getting the camera to focus and then realize I had moved the collar on the lens to the manual focus position. Since the aperture was on the smaller size I had a feeling I could prefocus on the grass and wait for the dog to arrive at that spot and the picture would be in focus. It worked well!