[MF3D.FORUM:1371] Re: build your own medium format stereo camera, cheap and easy

[Brian Reynolds <reynolds@xxxxxxxxx>]

Paul Talbot wrote:
> L wrote:
> > There is a 6X9 medfrm cardboard pinhole camera kit
> > that you can get for around $30.  It is made by
> > Besller.  IT is a fun camera, and if you strap it into
> > a tripod, it can take sharp pictures from about 2
> > inches to infinity.
> 
> How sharp?  I've not seen many pinhole photos, but
> what I've seen, though it had a large DOF range,
> was not at all sharp.  A friend I showed it to
> said that was typical of all pinhole shots he'd
> seen: very soft, but consistently so over a wide
> depth range.  Maybe it's just that neither of us
> have seen the best of pinhole photography, but until
> I see something dramatically sharper I'll remain
> skeptical of how well it would work for MF stereo.
> 

Pinhole pictures can be very sharp.  On page 16 of the first edition
of Eric Renner's "Pinhole Photography: Rediscovering a Historic
Technique" there is a pinhole picture of the Old State House in
downtown Boston by Roy Hines that looks like it was taken with a lens.
It was taken with a pinhole on 8x10 film.

There are several things that lead to sharp pinhole pictures.
Probably the two most important are that the pinhole must be on very
thin material and the hole must be round and burr free.  A popular
material is brass or steel shim stock (0.001-0.003 inch thick) from an
automotive supply store.  Examining the hole with a high power
magnifier (or a slide projector or enlarger) will let you determine
its quality.

The larger the film format the easier it is to get sharp pinhole
pictures.  Personally I don't think you can get sharp pictures on 35mm
film because you have to enlarge them too much to view them.  I'm
happy with enlargements from 4x5 negatives and I have also done 6x9
(including using the camera that Lincoln wrote about).

There are several formulas for optimizing pinhole size vs. film to
hole distance to get sharp images.  If you go to
<URL:http://www.pinhole.com/> you'll find a paper by Matt Young in the
"Resources" section that includes the derivation of a formula to
optimize pinhole size based on diffraction and resolution limits.  You
can also find the pinhole mailing list at that site.

I think the biggest reason that many people have never seen a sharp
pinhole picture is that most people taking pinhole pictures are not
trying to get sharp pictures.

> Also, what about exposure times?  Aren't they very long
> with pinhole photography?  Seems like you'll be restricted
> high speed film (not good for stereo) or to static subjects.
> At least until that Provia 400F comes out.
> 

My exposure times run from under a minute (perhaps as quickly as a few
seconds in bright sunlight) to tens of minutes.  I generally don't
have enough patience for exposures longer than about 30-45 minutes.  I
tend to use ISO 100 films (T-Max 100 and Ektachrome 100 Plus),
although I occassionally use faster film (T-Max 400, E200, and E200
pushed to two stops to EI 640).

Depending on subject, long exposure times can be an advantage.  I like
architecture without people.  The long exposure times of pinhole (and
large format stopped way down) can remove the people if they are in
motion throughout the exposure.

There is a pinhole photography section on my home page.  Included is a
series of comparison pictures of the same scenes shot with a 150mm
f/5.6 lens and an pinhole optimized for 150mm.  Unfortunately the
scans are not the best.

I would strongly recommend that anyone who wants to work with pinholes
read Eric Renner's book.  It has all sorts of information on history,
technique, and examples from many different photographers.

-- 
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"