>While I agree with Larry (separate post) that all of this math can be "over
>done" in the case of something as "hit and miss" as pinhole:
Well, let me make myself a bit more clear. I don't regard pinhole as
being "hit and miss" at all; that's not really what I said (I hope the
quote marks weren't quoting me!). If you think that I am advocating an
attitude of imprecision when approaching pinhole photography, I think you
misunderstand me pretty seriously. What I do mean is that there is a
very broad continuum between the art and the science, and the
interpretation (art) is at least as important as the calculation
(science). I calculate my holes carefully, too. But the application of
the specific pinhole really may be more important than the particular
number you may happen to believe in.
Actually, I did a series of practical tests for a studio in NY some years
back, shooting polaroids of newspaper text with various carefully made
holes. I began with the formula I got from the _Photo Lab Index_ which
was d=sqrt(.00007f), where d is the diameter of the hole and f is the
distance of the hole to film (my own rewording of this formula). This
may be similar to what you have; I'm not going to calculate it out for mm
- if you care enough about it, you can do that yourself. What I found
was surprising. The smaller the hole, the better the resolution, as far
as I went, and I got the factor represented in the formula by the .00007
down well below .00005. I don't remember how far down I went, but it was
quite a way down, to where the f/numbers were truly impractical. Being a
non-scientist, I must rely upon my incredibly human eyeballs. Doing so,
I very definitely saw what I am telling you I saw. And since I have made
a long career of looking carefully at things, I fairly well trust my
ability to see it. I did this without calculating what I was supposed to
see. I just saw.
Now, I'm sure that the diffraction increased, as well, but the smaller
holes had clearly finer resolution. This suggests to me that diffraction
and resolution are not part of a monolithic notion that can be reduced to
some single idea of "sharpness", but indeed are two distinctly different
things that coexist in varied proportions in every pinhole image and
which account for the distinctly different look and feel of images made
by various artists using different cameras of their own making. This is
what I'm talking about when I mention "sharpness within softness". In
practice, now, I'm using .00005 most of the time, but, as I say, I have
to consider very carefully just how I'm going to use this number. To
what point on the film do I measure? Well, I get to decide. There's a
lot more to it than applying a formula. You have to decide how to apply
it. The formula is only a place to start.
Now, what this means in real life is that different holes produce results
that LOOK DIFFERENT in real and tangible ways and one might like the
results of one better than the results of another. Or, one might choose
one over another for a specific application. To my way of thinking, the
idea that there is an "ideal" compromise between the Scylla and Charybdis
of resolution and diffraction is a gross oversimplification that
inevitably implies the outcome that everybody's images will - or should -
look pretty much the same if we did it right. Just as they very often
tend to look a lot alike when we all use the first rate - & wonderful -
camera lenses that the manufacturers are giving us. Not saying that
everybodys' images do look the same, but that the differences do not
derive from the technical image quality. They derive from our own true
vision -- which is in no way the result of calculation, however precise.
All of us are out there applying this ideal formula to our pinholes. We
never dream of actually trying something that doesn't conform to the
unconscious convention that we've established, based upon the concealed
assumption that "sharper is more good". We are trying to get our
pinholes to perform as much like lenses as possible, to meet some kind of
theoretical standard. They will always fall short because let's face it,
lenses do that better. The medium of pinhole photography will be doomed
to be merely a novelty. To me, this is a fairly course and simplistic
attitude. Pinhole appeals to me so much because there is so much to be
done with so very little.
Rather than proposing that we don't need to apply precision to something
as low-tech as pinhole photography I am suggesting that in this simple
optical device, the pinhole, there is 'way MORE than meets the rational
mind. I mean, the mind is an utterly inadequate tool, by itself, to deal
with the challenges it presents. It is not less complex, but in some
important ways, more complex. So complex, in fact, that only our
intuition can handle it.
Larry Bullis
Skagit Valley College