Re: flash duration

[ADavidhazy <andpph@xxxxxxx>]

I think that what Alberto suggested re: CD player or such running at  
7200 RPM just might work if its cover is black (paint it?) and put a  
white stripe along radius. It will be running at 120 RPS or close to  
it (wow that seems real fast!) or about 4300 degrees per second so a  
1/1000 second exposure time should leave an arc of about 43 degrees.  
But I suspect the flash will last longer than  that and also that the  
output of the flash is not constant. It should show a fast rise time  
and then a longer decay time. Duration is typically expressed as time  
for 1/2 peak to 1/2 peak so it will be less than the total length of  
the arc ... you should see a tapering off of the light output along  
the blur.

It is surprising how long flash durations really are when you give a  
more realistic estimate of this at 1/10 to 1/10 or so of peak output.

Now what else might make a good measuring stick for this .... falling  
objects as he suggested also. Chris's suggestion is a bit extreme but  
interesting. A car going past you at 60 mph carrying the flash and  
firing it as it passes by a camera with open shutter? Hmmm got to  
think more about this.  ;)

FWIW,
Andy