RE: Calculating accumulated flash for my pinhole camera...

Thank you for the input. I will post results shortly.
-Steve
 

-----Original Message-----
From: pinhole-discussion-admin@pinhole.com
[mailto:pinhole-discussion-admin@pinhole.com] On Behalf Of G.Penate
Sent: Thursday, December 06, 2001 8:37 PM
To: pinhole-discussion@pinhole.com
Subject: Re: [pinhole-discussion] Calculating accumulated flash for my
pinhole camera...

----- 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

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Received on Fri Dec 7 00:11:33 2001