Originally posted by Class A That's not correct.
One can use a neutral density filter and a sufficient amount of fast firing flashes (like the Einstein strobes). That may be a lot more unwieldy than using HSS as more stopping power is obtained by reducing flash power which means an increase in number of strobes used, but it is certainly possible and will lead to better results.
I didn't mention ND filters because they obviously cannot solve the problem in real life.
When freezing action outdoor against the sun, only the shadow parts are meant to be illuminated by flash. Therefore, the sunny parts would become blurred when using a flash at XSync shutter speeds. That's why I always included "outdoor" in my postings above.
If an ND filter would work, these HotSync flashes wouldn't have been created at all.
Regarding flash efficiency, the ND filter approach does NOT require more flash power than HotSync. True, the ND filter eats stops, say 5 stops for an ND5 filter. But the same holds true for HotSync where only a 1/32th-wide strip illuminates the frame (at 1/8000s). Note that only a single full strobe charge can be fired during an exposure, be it HotSync or traditional. That charge is 1000Ws with PrioLite, 500Ws with PrioLite or Profoto, or considerably less with hot shoe HSS flashes.
This means an MBX500 (non HS) with ND filter yields the same photos as the more expensive MBX500 HS version for more static subjects as model posing for fashion.
The difference comes from the requirement to freeze action outdoor. People pay for this feature for a reason. E.g., because ND filters can't do the trick ... And reflectors often don't do too, esp. when they make the models blink.
To tell the truth you seem to miss, nothing else does the trick.
Last edited by falconeye; 06-09-2015 at 04:37 PM.