From: Joachim Oppenheimer (joachim@microdsi.net)
Date: 04/12/02-05:22:59 PM Z
Let me relieve you of understandable guilt, confusion and frustration. I
have been exhibiting pinhole work and constructed the guts and pieces of
pinhole cameras. Forget the formulas, they will not work. I am a scientist
by training and constructed my cameras with micrometers, examined pinholes
under the microscope and measured them that way. I calculated lens-to-film
distances. I metered. The length of exposures with pinhole and the
variability of light, especially when working at the toe of the film curves
(usually below the toe, in the cellar) makes so-called scientific
measurement as sensible as measuring the length of Yankee Stadium with a
pocket ruler. Forget it. Set up trial conditions and keep superior notes of
your timing and light conditions (I use a "shadow exposure scale," i.e., how
black are the shadows, on a scale from 1-10?) I ALWAYS keep my darkroom
conditions as constant as possible. How good are my results? Most of my
negatives give me satisfaction, some give me "creative" surprises, many bomb
out. I get much more predictable results with my TTL metering of my
conventional hardware, but that's shooting fish in a barrel and not nearly
as much fun. Hope this helps. Joachim
> -----Original Message-----
> From: shannon stoney [mailto:sstoney@pdq.net]
> Sent: Friday, April 12, 2002 6:35 PM
> To: alt-photo-process-l@sask.usask.ca
> Subject: figuring pinhole exposures
>
>
> I recently read a formula for figuring pinhole exposures that I can't
> figure out. It goes as follows:
>
> -Set your light meter to an f stop and call it A.
> -The meter will give you an exposure time that you call S.
> -Figure your pinhole aperture and call it B.
> -Now find the correct exposure time with the formula and call it X
> -S B 2/A 2=X
>
> My questions are:
>
> 1. what number do you use for the pinhole aperture? the fraction of
> an inch that it is (like say 1/64) or its measurement in decimals
> (0.0156) or the f stop that it is (420)? I am thinking probably the
> latter.
>
> 2. IS SB2 the numerator and A2 the denominator? If so, why is there
> a two in the numerator and the denominator? Don't they cancel each
> other out? How do you figure this formula, in practical terms?
>
> 3. Is there a pinhole list?
>
> --shannon
> --
>
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