Originally posted by Wesbo If your pics are all white at F2 and 1/180, they will still be all white at F2 and any other faster shutter speed. The flash dumps all of its power in less than a thousandth of a second. Long story short: shutter speed will have NO effect on the flash exposure.
Chances are the photo is all white BECAUSE of the ambient exposure, and NOT the flash exposure. If they turned OFF the flash and also shot at f/2 1/180s (and whatever ISO they used, hopefully not ISO1600
) they would probably get a very similar looking photograph (all white!)
So in this case, you could either use a faster shutter speed provided you have an external flash that supports HSS, OR stop down the aperture so your ambient exposure is not being blown out.
So your assertion that "shutter speed will have NO effect on the flash exposure" is indeed correct, BUT in 99% of these cases it's the actual ambient exposure that is causing the blowout.