From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Newsgroups: rec.photo,alt.models
Subject: Re: looking for information on pinhole photography.
Date: 19 Aug 1992 19:04:14 GMT
Organization: Lawrence Berkeley Laboratory, California
NNTP-Posting-Host: 131.243.192.10

In article <1992Aug19.031500.28649@panix.com> reynolds@panix.com 
(Brian Reynolds) writes:

>Is there
>anywhere that I can get more information on pinhole photography.  Most
>of the books I've seen mention the pinhole lens while explaining the
>operation of normal lenses.  The one or two books I've seen that go
>into actually using a pinhole lens state that the sharpness suffers
>when using a pinhole.  The pictures in the IPMS article are much
>sharper than any of the pinhole pictures in the general photography
>books.

Rudolph Kingslake's new book (Is it Optics in Photography?) covers the
subject well.  Here is something I wrote a while ago in response to a 
similar question:

This is a brief? 8-) note from a NON-expert for those who haven't used pinholes
as imaging devices before.  My camera is an adaptation of an old 4x5 camera.
The resolution (and I realize most pinholers aren't striving for resolution)
is easily better than what you would expect from a dinky format (say Kodak
Disc).  Nevertheless, the pinhole gives a really unique softness.  The depth
of field, of course, is astounding.  I have a picture of my son with his face
nearly pasted to the pinhole and with a tree 1/4 mile away in the same shot.
The face and tree limbs both have good resolution.  Very exciting for me.

According to an article by a fellow named Connors in the _Pinhole_Journal_,
optimum resolution under average conditions is achieved when the diameter
of the pinhole is related to the distance of the pinhole from the film as
follows:

 diameter of pinhole in inches = .0073 (approx.) times the square root of 
                                 the distance from pinhole to film in inches

Connors found the constant in this formula by experiment.  It is very close
to what you would find by theory (setting geometric spot size = diffraction).
The reason that there is an optimum pinhole diameter is that as the pinhole
diameter is decreased, the resolution on the film gets better due to the
obvious geometric effects but at the same time it gets worse due to diffraction
effects.  As a result, there is a fairly broad range of acceptable pinhole
diameters but the best resolution is found when the pinhole is sized by the
formula given.  

There is also another effect, which I'm not sure I can prove rigorously so
I won't attempt it, and that is that the larger the film format, the higher
the resolution.  Basically, keeping the angle of view the same, as the film 
size goes up, one uses a greater distance from pinhole to film, but the size
of the pinhole goes up as the square root of that distance so it's not
increasing very fast hence resolution goes up.  I'd love to have an
8x10 pinhole camera, but I can't afford the less common and hence more
expensive film, film holders, etc.

I have an old 4x5 camera, a Crown Graphic, which can be had cheaply anywhere.
Someone gave me a messed up Wollensak "Alpax" shutter which I restored to
more or less working order.  I mounted the shutter on a lens board which fits
the 4x5, mounted a pinhole on the front of the shutter and a Polaroid 545
film holder on the back of the camera and presto, I've got a pinhole camera.
I use Polaroid ASA 400 black and white film.  Obviously, one doesn't need
all this stuff to make a pinhole camera, but I sure think the Polaroid back
is a really nice thing to have as a starting point.  The shutter is just a
convenience; an old felt hat will do just as well.

I wanted a few different pinhole sizes to use with the 4x5.  I decided on
three pinholes; the optimum distance from the film plane for the middle 
hole is about twice and half the distance of its smaller and larger mates,
respectively.  I decided the middle pinhole should be for around 6" operating
distance.  By the formula: diameter = .0073 SQRT 6 = .018 inches.  I found
I had a drill with a diameter of .018" so that was the middle-sized drill.  
Similarly, I used drills  of .0135 and .024 inches.  These drills are easy
to get.  They are members of the American number drill series.  The .024"
drill is a #73, the .018" drill is a #77 and the .0135" drill is a #80.
They're available at machine shop supply stores.  (#80 is the smallest
that's readily available.)

Drilling the holes is really not too tough.  I got some.001" brass shim stock
(available at machine shop supply houses and some automotive supply houses).
I clamped the shim stock between two 1/16 inch thick layers of sheet aluminum.
I put the drill bit in a Sears "Lil Crafty" (a Moto Tool or Dremel tool
would work as well) and drilled through the assembly.  There was a barely-
perceptible burr on the hole which I removed with 600 grit wet and dry
abrasive paper (available at the same places as those which have shim stock).
I then painted the interior of the hole black by daubing it with a felt pen.
You can also dent a piece of shim stock with a needle and abrade away the
bump until a small hole peeks through.

Exposure is not too difficult either.  Just remember that the definition
of f/number is merely the distance from the pinhole to the film plane divided
by the diameter of the pinhole.  For my .018" pinhole used at a distance of
6", the f/no is 333.  For my first exposure, I just read my Luna Pro F
light meter and figured what the exposure would be for f/333.  It turned
out to be 3/4 second for ASA 400 so that's what I set the shutter for.  I got 
a perfect exposure on the first try!  The "Sunny 16" exposure rule would
work just as well if you have negative film and hence a little latitude.

The upshot is that if you haven't tried a pinhole camera, it's easy and yuh
oughta!

John Bercovitz     (JHBercovitz@lbl.gov)

Newsgroups: rec.photo