Re: Re: Bellows factor

----- Original Message -----
From: "Colin Talcroft" <ctalcroft@yahoo.com>
To: <pinhole-discussion@pinhole.com>

> By the way, the formula I eventually used simply says
> divide the square of the new length by the square of
> the old length to get the bellows factor, so in my
> example that was 32.5 centimeters squared (1056)
> divided by 5 centimeters squared (25) equals 42.25. So
> 42.25 times my original 2 second exposure at 5
> centimeters is 84.5 seconds--more or less the same
> answer others reported but by formulas that seemed
> more complicated (to me anyway).

Colin, remember that the square of the new length divided by the square of
the old one is the same as dividing the new length by the old and squaring
the result, this way, if you have to do it by hand, you will be working with
smaller numbers. This is the formula I said when Guy asked me to expand on
my answer:

Time Factor = ( B2 / B1 ) ^ 2

B1 = old length and B2 = new length

Anyway, just thought to let you know.

Guillermo
Received on Tue Dec 4 08:53:09 2001