> The solution I came up with was the use of a Waterhouse stop with a very
> small aperture to replace the iris diaphragm in a conventional lens. I
made
> a 1 mm Waterhouse stop using the usual pinhole technique with sewing
needles,
> sandpaper, etc. as has been recently described on this list. The brass
shim
> stock was too flimsy to use without some sort of reinforcement; so, I glued
> it to a piece of wood veneer 1/28" thick as a support. I painted the
entire structure
> black.
The Waterhouse stop is simply a disk which has a hole in the center of it--in
this case, a pinhole. These date from the mid-19th century, before the
invention of the iris diaphragm. Many lenses from that period were supplied
with a series of disks with apertures of varying size. A disk with the
desired aperture was inserted through a slot in the lens barrel into the
optical center of the lens and functioned just as a modern adjustable iris
diaphragm does.
The lens I use for the pseudo-pinhole is a modern view camera lens (135mm
Symmar in a #0 Compur shutter); any lens mounted in a shutter should do just
as well. If you screw off either the front or the back element, the
diaphragm and shutter are exposed. I made my pinhole diaphragm as a disk
just the right size to fit into this space. It may require a bit of
engineering with sandpaper and files etc. to get it to fit properly; this
should be no problem, as brass and wood veneer (or cardboard, very thin
plastic, or whatever support material you want to use) are soft and easy to
sand. You obviously don't want it to fit **too** tightly, as it could be
difficult to remove if it gets lodged in the shutter.
So, after composing on the ground glass, I screw off the front half of the
lens, open the diaphragm completely, drop in the Waterhouse stop, and screw
the front element back on (not tightly, in order to avoid damaging the
shutter and diaphragm). The effective f stop is easy to figure: with a 1 mm
aperture, measure the distance from the film plane to the center of the lens
in mm, and that is your f stop (f = focal length / aperture).
I have used this only for macro work. But, I see no reason why it shouldn't
have the same effect with the subject at a more conventional distance from
the camera.
Hope this clears things up.
Charlie Palmer