bmacphoto: The case I was referring to was when you have studio flash units at full power, in some cases the flash duration might be as long as, say 1/340 sec. If you use a shutter speed of 1/500 sec., the flash duration will be longer than the time the shutter is open. There is no particularly good reason to use such a high shutter speed in the studio anyway, since the flash is likely to be so much more powerful than the ambient light, that you could use a sync speed of 1/15 sec. or even slower in some cases without noticing a difference.