Its difficult to answer if you keep changing the question
Flash sync speed is a function of camera / shutter design. The focal plane shutter camera can\'t instruct the flash to fire until the first curtain of a focal plane shutter fully opens, which typically takes about 1/500th to /400th sec. Flash fires, second curtain closes. When the shutter gets to fast the shadow of the second curtain is recorded. The specified x-sync speeds can often be exceeded, but not by any great amount. Cameras without focal plane shutters can sync at higher speeds because there\'s no shutter curtain to wait for.
But if you want to stop fast action with a DSLR you can use a different strategy. Reduce the ambient light so there will be no blur trail ( a totally dark room is best) use a long shutter speed, then fire the flash manually to make the action stopping exposure. In that scenario the power level used will determine the flash duration. As mentioned previous hot shoe flashes work best for this because they have shorter flash durations.
High speed sync mode, which pulses a hot shoe flash rapidly, works well for shooting at wide apertures in bright outdoor light, but its not the tool you\'d want to use to freeze action.
Chuck
Chuck
Mar 14, 2009 at 11:45 AM
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