----- Original Message -----
From: "William Erickson" <erickson@ic.mankato.mn.us>
> I just divide the area of the pinhole (pi times radius
> squared) into the area (ditto)of the F22 aperture (diameter that is 1/22 of
> the distance from pinhole to negative) and multiply the result times the
> metered exposure at F22, then correct for reciprocity failure. Someday I'll
> find someone else who has also turned away from the altar of F stop.
The f/stop goddess may not seem to be there, but her "ghost" still haunts you, see that 1/22 above? that's her!
As I am pretty sure you know, there's no need to find AREAS -per se-, simplifying (mathematically) your method, you are just dividing the focal length of the pinhole camera by the result of multiplying the F/STOP you take the reading in your meter at by the diameter of your pinhole and finally squaring the result
FACTOR = [ Focal_length / (meterFstop * pinholediameter) ] ^ 2
Guillermo
Received on Sat Jul 21 09:19:00 2001
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