Re: [photo-3d] Moving, and making pin holes, or buying them

[Brian Reynolds <reynolds@xxxxxxxxx>]

Lincoln wrote:
> I have seen some pinholes for sale, but they cost to
> much.  I was hoping to get them for just a few
> dollars.  Are there ones that cheap?
> 

Others have already mentioned Pinhole Resource.  I would strongly
recommend getting a copy of Eric Renner's "Pinhole Photography:
Rediscovering a Historic Technique".  Eric runs Pinhole Resource and
you can buy the book from them.  You can also talk to them about
getting custom pinhole sets rather than buying two sets with lots of
duplicates.  Pinhole Resources also sells a series of 4x5 and 8x10
pinhole cameras.  They used to sell a 4x5 stereo pinhole camera (two
images on one 4x5 sheet), but I don't see it listed anymore.  You
might want to ask about that too.

If you want to make your pinholes there are two things that are very
important if you want good resolution.  The hole should be round and
the material should be thin.  I use thin brass sheets from the hobby
shop.  Others use steel shim stock from automotive supply stores, and
some use hammered silver sheet (which can be chemically blackened with
selenium toner) from a jeweler.  Anything from .001 inch through about
.003 inch will be fine.

Although I've had some luck using very fine jeweler's drill bits
(available from Micro Mark and hobby shops), there is an easier way to
make a good hole using a beading needle, a sewing needle and fine
emery cloth.  Put the metal sheet on a piece of cardboard and make a
dimple.  Now gentle drill a hole in the dimple with the sewing needle.
I put the needle in a pin vice.  Do not push the needle all the way
through the sheet.  Now you can measure your hole and adjust its size
(and remove burrs) by rubbing it on the emery cloth.

There are various formulas for picking the "optimum" pinhole size.
Many years ago I saved a posting from John Bercovitz with the
following formula:

pinhole diameter = .0073 * sqrt(pinhole to film distance)

All measuremens are in inches.  The constant is approximate and
different people use different values.  I only have a print out of
John's post (which was the first thing I could lay my hands on), but
if you are interested I can dig up more "rigorous" proofs involving
the diffraction limit and the Raleigh resolution limit.

There are several ways to measure and inspect your pinholes.  I used a
pocket microscope with a measuring reticle from Edmund Scientific.
You could also mount the pinhole in a 2x2 slide mount and project it
on a screen.  By first projecting the image of a ruler (perhaps a
clear plastic ruler) you can figure out the image scale and then
calculate the pinhole size.  If you can an enlarger you can use that
instead of a slide projector.

For lots more information (including an article by Matt Young on the
Physics behind pinholes (with the above mentioned proof), more on
making pinholes and infomation on the pinhole mailing list) check out
<URL:http://www.pinhole.com/>.

-- 
Brian Reynolds                  | "Dee Dee!  Don't touch that button!"
reynolds@xxxxxxxxx              | "Oooh!"
http://www.panix.com/~reynolds  |    -- Dexter and Dee Dee
NAR# 54438                      |       "Dexter's Laboratory"