----- Original Message -----
From: "Steve Wilson" <steve.wilson@eyeconcur.com>
> If my camera's pinhole f-stop is F197 and my metered strobe reading for
> the scene is F22 (assuming correct meter reading for film ASA), I would
> have to hit the flash approximately 8 times (22,32,45,64,90,125,180,250)
> to get a correct exposure for the image?
Michael Keller gave you a correct answer already. Another way to find the
number of flashes is dividing the pinhole aperture (f/197) by the meter
reading aperture for your flash (f/22) and then squaring the result. This
way:
Number of flashes: ( 197 / 22 ) ^ 2 = 80
This number of flashes is valid "only" when the flash does not change
position for all the 80 pops.
Also, something called "intermitance" states that although mathematically 80
f/22 flash pops are equal to 1 single BIG flash pop of f/197, in reality,
the effect of 80 f/22 pops is less than 1 BIG f/197 pop. Sort of like a
"reciprocity failure for flashes". Some more extra flash pops should be
added to compensate for that "intermitance" effect.
Guillermo
Received on Thu Dec 6 23:30:48 2001
This archive was generated by hypermail 2.1.8 : Mon 13 Dec 2004 - 23:33:31 PST