 Due to its hybrid electronic/mechanical shutter, it is in fact possible to flash sync the D40 beyond its published 1/500 maximum sync speed up to its maximum shutter speed of 1/4000.The D40x does not share this ability.The D40 lacks a built-in autofocus motor, which means that only Nikon lenses designated with AF-I, AF-S or compatible focus motors can be used in autofocus mode.