You will probably be advised that pinhole images are too fuzzy to
enlarge. Whether you believe this or not is up to you. I can speak from
my own experience. Two examples, from many I could offer:
1. About ten years ago, I was commissioned to do a series of posters for
the Tacoma/Pierce County Convention and Visitor's Bureau. One of these
posters was made from a 4x5 (inch) pinhole transparency. The finished
image size was approximately 14 x 17 inches, and was actually cropped
from an approximately16 x 20 inch enlargement. The poster was produced 6
color; that is, it was printed with four color, a varnish, and a border
in a neutral gray. It was quite an expensive production, and frankly, in
my own biased opinion, is one of the truly outstanding pieces of my
entire career. No one would ever know it was pinhole unless they were to
understand the diffraction rainbow that permeates the whole image. It
looks like it was made by magic. Sharpness is no problem.
2. You may be familiar with the image on the cover of Eric Renner's book
_Pinhole Photography: Rediscovering a Historic Technique_. This is my
image, and was made from a 4x5 pinhole (oddly enough!) color negative.
Whether this is acceptably sharp for you, you can judge for yourself.
The book is 8.5 x 11 inches. Granted, since it is a reproduction, you
may be reluctant to accept what you see as representative of a
photographic enlargement the same size. I have an enlargement of the
same image that is (I'm not going to measure it right now, but this is
close enough) 18 x 22 inches, and again, it looks really great. There's
a kind of mediocre scan of this image (hope to have time to replace it
soon) on my website at "
http://www.halcyon.com/cif/Kingfisher/Photo/Pinhole/daff.html ". This
won't tell you much, but if you can find a copy of the book, maybe you
can get a better idea.
It seems to me that even alt photographers tend to buy into the
conventional bias toward "sharp" that dominates our culture's use of the
image. Pinhole images have another quality which on its own is quite
worthy of appreciation. Enlargement doesn't really detract from it, in
my opinion. If you measure it rigidly against the standard of lens
imagery with a single minded determination to make it conform to that
standard or fail, then of course it will fall short. Sometimes I get the
idea that everybody but me secretely photographs test charts all the
time; I never do. What do these nubers really have to do with anything?
If you can take the pinhole image on its own terms, you may be surprised,
if not absolutely astonished, at what it has to offer. There can be a
surprising sharpness contained within that veil of softness.
If there is one factor in achieving the best quality (again, quality on
the terms of the pinhole itself) of the image, it would be in the making
of the pinhole itself. I don't think exact conformance to formula for
the size has anywhere near the importance of clean edges, roundness, and
sharpness (as in knife-edge) of the pinhole itself. Drilled holes are
inherently (vastly) inferior for a number of reasons. I make my holes in
pure silver foil with a needle and use jewelers' files and even
sharpening stones to get them sharp, and I have a projection microscope
which I use for measuring and making sure the edges are perfectly clean.
Then I blacken them with selenium toner. This gets rid of some of the
internal reflections that degrade the image.
Also, the formulas really don't have a lot of utility, except as a guide
(unless you are just into numbers for their own sake). Every point on
the film has something of a different "focal length" anyway, so the
formula usually applies only to the point in the center, or the point on
the film which falls on the optical axis of the hole. The actual size of
the hole is really, whether you are willing to accept it or not, a
compromise. Most of my cameras are eccentric (the hole is mounted
severely off-center and at a slant), so this becomes a big issue. Just
which point on the film am I going to use to calculate the size for?
Distance of hole to film may vary from less than 1 inch to about 6 inches
at different points, depending on where you choose to measure.
I've already used up my bandwidth allocation for the month. Hope, in all
of this, there's something you can use.
Larry Bullis
Skagit Valley College