I bought one from the Pinhole resource group. It's an OM body cap with a
precision, pre-made pinhole in the cap. (Despite what they say, it's not
an OEM Olympus cap, but that doesn't really matter.)
From: http://www.pinholeresource.com/:
< Precision-made body caps, made from converted manufacturer's caps, have a
.259mm pinhole, approx. focal length of 50mm, approx. f/185, and fit the
following
cameras:
<Price: $40 postpaid, ($45 foreign air)
Nikon (all models)
Canon EOS
Canon F
Pentax Screw Mount
Minolta Maxxum
Olympus OM
Mamiya 645.
I've not had a chance to use it yet.
Skip
At 7/10/99 10:00 PM -0500, you wrote:
>Date: Sat, 10 Jul 1999 08:33:39 -0700
>From: Norma Foltz <flzhgn@xxxxxxxxxxxxx>
>Subject: [OM] I like the Zuiko 4.0/200mm
>
><snip>
>_____________
>
>Now a question for the OM group:
>
>Does anyone have recommendations for making a pinhole that can be used on
>an OM camera or any examples of pinhole photos done with an Olympus Camera?
>
>I am thinking of making a pinhole attachment that I can use with my Olympus
>extension
>tubes, etc.
>
>Hank Hogan <flzhgn@xxxxxxxxxxxxx>
>----------------------------------------------------------------------------
>--------------------------
>
>Norma,
>
>Title says it all. I found this in a site on amateur telescope making, and
>thought I would pass it on. I haven't actually tried this, but the method
>seems
>to make a lot of "horse sense" to me.
>
>regards,
>
>Mahlon
>
>----------------------------------------------
>
>How to Make Precision Pinholes
>
>Conducted by Roger W. Sinnot
>
>Cribbed without permission from Gleanings for ATM's, Sky and Telescope May,
>1981
>
>
><background info snipped>
>
>Let us turn to the New Photo-Miniature, where the directions are given:
>
> Before we can make the needed pinhole, we must have the needles of the
>right size. SInce the beginnings of
> pinhole photography, three sizes have been most generally used, No. 10,
>about 1/55 of an inch in diameter, No.
> 11, about 1/65 of an inch, and No. 12, about 1/75 of an inch in
>diameter...
> FOr use, the needles should be
> forced, eye first, into little sticks or holders about the size of a lead
>pencil, or a fine pin-drill may be used as a
> handle...
>
> Metal pinholes may be made of copper, brass, aluminum or even silver.
They
>may be made in two ways, using
> rather heavy, 24 gauge or so, metal or using very thin metal and mounting
>the finsihed pinhole on thin card or
> fibre...
>
> If the heavier metal is used, we must first cut a cup-shaped
depression in
>it by starting to drill with a 1/4 inch or
> 5/16 inch twist drill, stopping just before the drill begins to go
>through.
> We must be very careful not to puncture
> or tear the metal with the drill, but we do want to get the bottom of the
>depression as thin as possible. After the
> depression is made, the procedure is just the same whether we use the
thin
>metal or the thick.
>
> The metal is laid on a yielding surface, like several thicknesses of
>blotting paper or a piece of linoleum. With a
> blunt rounded point like that of a used lead pencil and gentle
pressure, a
>dent is made in the bottom of the
> depression or in the center of the pice of thin metal. The metal is
turned
>over and the bump raised by the pencil
> point is gently rubbed away, even with the surface, with a fine
sharpening
>stone or a smooth file. This results in
> a very thin spot in the center of the metal. The metal is now turned
>face-up again and laid on a block of wood
> or a piece of cardboard. The thinnest center of the metal is now just
>punctured with the point of the selected
> size needle. This raises a burr on the back, which is rubbed away with the
>stone or file. The needle is pushed,
> not twirled or twisted, through a little farther and the burr is rubbed
>down. This is all repeated until the needle
> passes through smoothly to its largest diameter. The needle-hole should
>now
> be polished gently with the
> sharpened point of a toothpick, very gentle because the edge is very thin
>if properly made. The needlehole
> should be blackened with India ink or dull black lacquer, but
>preferably by
> heat and fumes from sulpur or a
> burning match. The edge of the aperature must be blackened, above all
>else,
> to avoid stray reflections.
>
> Examine the needle-hole with a magnifier and run the needle, used in
>making, through the aperature carefully
> to clean out any matter resulting from the blackening process.
>
> For the rubbing down of the burr, various implements may be used; the
>principle thing is to rub lightly. Fine
> grained India, Washita, or Carborundum sharpening stones or hones may be
>used. An old style slate pencil,
> which is all slate and not cased in wood, is excellent if used deftly. It
>should be first rubbed down on sand
> paper or emery paper until it has a blunt bevel on the end instead of a
>point. Very fine emery cloth is one of the
> best things to rub down the burr; it should be wrapped around a little
>block of wood about the size of a
> domino...
>
>These sure, careful steps stand in sharp contrast to the hit-or-miss
procedures
>mirror makers have generally used to make
>Foucault pinholes in aluminum foil. Yet when I tried out the method on a sheet
>of brass 0.025-inch thick, it proved easy and
>fun to do, and gave exquisitely thin and circular pinholes. I now have a whole
>set of various sizes, for photographic and
>mirror making purposes.
>
>Among the old-timers, Rev. W. F. A. Ellison in particular waned against too
>small a hole in Amateur Telescope Making ---
>Book One (page 84) because diffraction effects might lead to misinterpretation
>of the mirror's figure. He and Russell W.
>Porter merely suggested a fine needle for piercing thin metal. G. W. Ritchey,
>who made the 60- and 100-inch materpieces
>for Mount Wilson Observatory just after the turn of the century, preferred to
>test with a 1/250- to 1/500-inch pinhole, much
>smaller than an ordinary needle can produce. Honing a needle to make it
smaller
>is described in ATM-2, halfway down on
>page 89; then the photographer's directions quoted could still be applied.
>
>The size of a pinhole for optimum photographic imaging was investigated by
Lord
>Rayleigh long ago. First he pointed out a
>plane parallel glass window will meet his 1/4-wave tolerance as a substitute
>for
> a lens, provided the focal length exceeds
>about 20,000 times the square of the aperature in inches. This being so, he
>noted, one can take away the window and use an
>opening of the same size instead!
>
>According to his formula, a 1/50-inch pinhole should be used at 8 inches or
>more, although in photography there is nothing
>really critical about this. A 1/4 inch "pinhole", which might be used to
>project
> sunspots on a screen in a dark chamber should
>have a throw of 1200 inches or 100 feet; the 11-inch solar image will show
>diffraction-limited detail likle that seen with a
>properly filtered 1/4 inch telescope (resolution 20 arc seconds. A heliostat
>and
> a long tunnel would be ideal for such an
>experiment.
>
>A cardboard tube with a pinhole objective atone end an an eyepiece at the
other
>becomes a pinhole telescope. I have tried
>such an instrument on landscapes by day and on the Moon, planets, and double
>stars by night, hoping to find out whether
>more can be seen this way than with the naked eye alone. I'd like to hear from
>readers who try the same thing.
>
>
>
>
>
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>
-----------------------------------------------
Skip Williams - skipwilliams@xxxxxxxxx
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