So I have a question regarding using fast shutter speed (maybe 1/500-1/800 would be nice) to stop motion on a prticular subject using a strobe (540EZ with some cheap wireless trigger). I can't seem to go any faster than 1/200 - is this just the limit of my gear (400d and 450EZ)? If so, which is the limiting factor? If not, how do I go faster? Thanks!