Thanks guys
Some interesting advice... I really need to buy a turntable! Lots of
uses in product photography, QTVR etc. plus this... Alberto, I'll do
the shots and send you the results to do the math/analysis :-) Actually
I've mixed up your advice and I think what I'll do is shoot a falling
black marble against a white background - continuous light at 1/3 stop
intervals from 1/250 up to 1/8000. Then shoot it in the dark with the
flash, and compare results...
The shutter is the most (Only) reliable timing device I have. I suspect
that the useful duration at minimum power is between 1/1000 and 1/4000
Is there fault in my reasoning?.. tell me
Herschel
On 1/28/11 9:16 AM, ADavidhazy wrote:
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
