Here the shutter speed is short enough to capture the set, including the man looking at the girls. But not fast enough to completely stop the motion of the girls. Canon 350D (Rebel XT) with 17-85 IS lens (~28-135)ISO 1600 1/10 @ F6.3 Focal length = 17 mm (28) Hand held. The lens is image stabilised (IS) which means it can be used with much lower shutter speeds.I would not expect reliable results at anything less than 1/30 of a second.