Dogs in motion are hard to get right without using professional equipment. Fast focusing lenses and a hight shutter speed are required, accurate focus as well. Meduim range DSLRs and consumer zooms don't always get the shot. In the old days you had to prefocus manually and wait for the subject to cross over, either that or take multible shots while manually adjusting focus. Good auto focus on pro level cameras can do an amazing job of nailing focus for fast moving objects. That is one of the main reasons pros buy the expensive stuff, for the high ISO performance and the state of the art auto focus systems as well as the newer fast pro lenses available.