The Speedotron Black Line 2400 watt-second has a flash duration of 1/300th second, and shorter if you dial down the power. That's typical of studio power packs. That duration is measured between the 10 percent points. I'm not sure why you'd care about latency (I have to admit I haven't been following this off-topic discussion closely). Latency (the time lag it takes for the light out put to reach 10 percent of its peak) should be measured in microseconds rather than milliseconds and should rarely be of concern.
In a message dated 10/31/2001 3:56:05 PM Pacific Standard Time, firstname.lastname@example.org writes:
> I thought the longest flash durations were in the neighborhood of
> 1/500th sec. I don't recall seeing exposure differences at shutter
> speeds 1/250 or slower where ambient light isn't a factor.
It takes "some" time for the flash to actually fire...and I would also guess
different types of flashes have different timing (latency). Does anyone
actually know what a typical flashes latency time is?
I can check my Elinchroms to see what they say this time is supposed to
be...as I have the service manuals for them, and they are pretty
comprehensive...hopefully, they'll have something to say about it.