Re: re: calculating exposure

----- Original Message -----
From: "John Yeo" <jonnieo@thegrid.net>
To: <pinhole-discussion@pinhole.com>
Sent: Friday, December 29, 2000 7:16 PM
Subject: Re: [pinhole-discussion] re: calculating exposure

> I didn't see it there. Where on the page is it?
>
> How does one calculate half stops? I tried adding 1/22 and 1/32, then
> dividing by 2, but i got f/26.07, not 1/27.25 like you got. I would like
to
> make a dial calculator with half stops

For one half stops less you multiply the f/stop by SQRT(1 + 1/2)

So one half stop less than f/22 is:

22 * SQRT(1 + 1/2) = 22 * SQRT(1.5) = 22 * 1.2247448714 = 26.94 aprox

Mathematically, though, f/22 is f/22.6274, therefore half stop less would be
= 27.71

So we can safely say that half stop less than f/22 is f/27

Guillermo
Received on Fri Dec 29 21:45:27 2000