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12-31-2014, 08:26 PM - 1 Like   #16
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Join Date: Feb 2014
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Posts: 1,350
I built a Flash Guide Number slide calculator.
I will update it with fold and glue marks at some time, but for now it works as is.

cut out the blue part, and use the slider under it to use it.

set ISO 100 to the GN of flash.
find ISO of film used, and GN idicated on top scale is the GN for that ISO.
Now set 100 ISO to that GN and read the distance/ f:stop scales as desired.

For instance:
My Holga flash has a GN of 72 but tests out closer to GN 65.
set ISO 100 under GN 65 (guesstimate the interval between 50 and 72)
My film is ISO 32, and so my GN is right at 36 at ISO 32.
I set ISO 100 under GN 36, and my distance at f:5.6 is very close to 6+ feet.

Anyways here it is if you want it.


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