Just a guess, but I would think the manufacturer would design a system in which the strobe was aware of the shutter speed so it didn't have to keep flashing once the shutter was fully closed. Big difference between asking the strobe to cover 1/500 seconds versus 1/8000.
I don't think that is what happens. The shutter always takes the maximum sync speed (say 1/250th) to open then fully close at high speeds. The slit between the shutters (the shutter is never fully open at higher speeds) creates the higher shutter speeds. So the burn of the HSS flash is always 1/250th or whatever but at higher speeds the maximum power is cut as the gap between the shutters narrows. The shutter curtains themselves always travel at the same speed it's the timing of the second curtains release that controls shutter speed. So what you would need to look for is a flash that burns for the amount of time it takes for the the speed graphic shutter to fully open and fully close. I don't know how long that takes with a speed graphic but if it takes 1/30 with a Pentax 67 I would guess it would take a 1/15 or an 1/8 second with a Speed. I don't know where you would find a flash that burns for that long.
Tin Can
I'm still on my first cup of coffee for the day, but how about this: Assuming Tobias is correct and that the total duration of the HSS flashes are within a 1/250-second window, then I should be able to use the Speed Graphic's focal-plan shutter at 1/250 or faster. I just need to figure out how to trigger the flash. Might start experimenting today. ...doug
Thinking about this some more, the frequency and magnitude of the pulses might be tailored to the shutter speed, though any of the sequences should work for a much slower curtain shutter - *if* the overall duration of the pulse sequence is long enough, which it probably isn't. Oh, well.
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