Re: Re: Bellows factor

I don't remember guillermo explaining it, so here's my shot at it.

Every time the bellows extension is doubled, you have to increase exposure
by 2 stops. If you extend the bellows by a factor of 1.414 (the square
root of 2), you must double the exposure.

so... sqr(2)^x = extension factor. x is the number of stops

He is extending the bellows by a factor of 6.5.

sqr(2)^x = 6.5
x log sqr(2) = log 6.5 logrhythm properties
x = (log 6.5) / (log (sqr(2)) simple algebra
x = 5.4

you must add 5.4 stops of exposure, so 2 * (2^5.4) is 84.44 sec. As for why
colin's exposures weren't matching this, i am baffled. Maybe he lives in a
part of the world where the laws of physics don't apply :P

John

So, you would have to multiply the exposure by 5.4----- Original
Message -----
From: "Guy Glorieux" <guy.glorieux@sympatico.ca>
To: "Pinhole List" <pinhole-discussion@pinhole.com>
Sent: Friday, November 30, 2001 3:14 AM
Subject: [pinhole-discussion] Re: Bellows factor

>
>
> "G.Penate" wrote:
>
> > just plain physics of light.
> > This case is in no way different than if you were using a glass lens.
> > <snip>
> > 84.5 seconds (uncorrected for reciprocity, time)
>
> Guillermo,
> Can you remind me how you worked this out.
> Guy
>
>
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Received on Sat Dec 1 00:41:35 2001