Re: 4 questions from a beginner

----- Original Message -----
From: "Bre Pettis" <pettisb@yahoo.com>

> Question 1
> I've got a .013 needle hole and 1&#34; from
> the hole to the film. I've got it loaded with 400
> speed b&amp;w film. How long should I try for
> an exposure on a sunny day? Am I right in gauging the
> f stop at f/77? I've got a light meter, should I use
> it and should I make any adjustment for using a
> pinhole?

If your pinhole is actually 0.013", yes f/77 is your f/stop. Once you know the
f/stop and speed of film, when it comes to find the exposure time, it is
irrelevant what camera you have (IE: cardboard pinhole or Hasselblad) as well as
irrelevant is which lens you are using (IE: a Carl Zeiss or a dirt cheap pinhole
lens) and what's the focal length of that lens. So if you got a light meter,
use it "business as usual". BTW, f/77 is equal to f/64 +1/2 stop, if I were
you, I'd approximate that to f/90. If so, "Sunny/16" says that under bright
sunny skies and using ISO-400, exposure should be f/16 and 1/400 secs, therefore
for your f/90 pinhole, the exposure should be 5 stops more.

> Question 2
>
> I've made a 250 sheet photo paper box pinhole camera
> with a .013 hole. I'm not getting nearly as much
> light around the edges as in the middle. I thought it
> might be the pinhole, so I made another with the same
> problem. Is lack of light on the edges normal?

Yes it is (as explained by erickson@hickorytech.net). The wider the angle of
view of your camera the more pronounced that fall off will be, even if you make
the hole bigger. Something else that contributes to make it worst is a not so
clean pinhole and a pinhole made on a very thick material.

Guillermo
Received on Wed Aug 21 10:06:23 2002