I would like to know if anyone has tried this:
Without an ND filter, use minimum aperture and lowest ISO setting, mount camera on tripod and take multiple shots of the waterfall. If each shot is 1/250 sec, take a total of 20 shots for a total exposure of 1/4 sec.
In PS, stack all the 20 shots and do an average.
Would that blur the water enough to mimic the long exposure achieved with ND filters?