RE: lith film, bergger film, cyanotype

["Gordon J. Holtslander" <holtsg@duke.usask.ca>]

Hi:

As the "focal length" of a pinhole decreases the fall-off for a flat film
plane increases.  Its like using a lens with not enough coverage.

If one makes a circular backed camera there is no fall-off.  If the back
is a perfect arc then the focal length of the camera matches the radius of
the arc.

I the arc is perfect then there is no fall-off.  All flat back pinhole
cameras suffer from some degree of fall off.  If the focal length is
long-enough it is not noticable.  As the focal length decreases fall-off
becomes more apparent unless the back is curved.

These cameras give an ange of view approaching 180 degrees.

I love round back wide angle pinhole cameras. I've used 4X10 to 12X18.
Plans for more in the works . . .  12x 48 :)

Gord

On Wed, 15 May 2002, Joachim Oppenheimer wrote:

> Please explain how a curved film plane can receive even exposure from a
> point (pinhole or lens, for that matter). Each point of the film is at a
> different distance from the pinhole so that the light fall-off differs
> accordingly. I would appreciate your take on this. Thanks in advance,
> Joachim
>
> > -----Original Message-----
> > From: Christina Z. Anderson [mailto:zphoto@montana.net]
> > Sent: Wednesday, May 15, 2002 10:06 PM
> > To: Alt Photo List
> > Subject: lith film, bergger film, cyanotype
> >
> >
> > Hi all!
> >      I've been experimenting with different lith films in a
> > pinhole camera,
> > and different developers.  I have used Arista APH and APHS (no
> > difference I
> > can tell...) in Howard Efner's nifty 4"x10" pinhole camera, with
> > an exposure
> > of about 48 secs Sunny 16.  It is an f269 camera.  He made it so that the
> > innards of the camera curve the film plane in a semicircle so exposure
> > is even.  Fun stuff (hopefully he will manufacture said
> > camera and sell it; the one he is letting me use is his prototype).
> >     A couple things I've found.  One is that it sure doesn't seem
> > that lith
> > film experiences reciprocity failure at those long exposure times.
> >      I used it at ISO 6 and 10; both work, but ISO 6 and development in
> > Dektol 1:10 for 2.5 min as per someone's recommendation on this list works
> > well.  at ISO 10 in Dektol 1:6 for 1.5 min it also works fine.
> > Pinholes are
> > now minimal without the weak acetic acid stop bath, just using water.
> >      I've been testing the negs out with some old cyanotype
> > solution--it is
> > Mike Ware's stuff, 3 yr old, goes on a bright chartreuse green but exposes
> > well and in about 5 minutes in full sun.  I tried it on kid finish Cranes
> > and it was terrible; bled and washed out.  On Platinotype it is
> > really nice.
> > I tested the solution to make sure it was working up to snuff by comparing
> > it to an old exposure neg that I had worked out 3 yr ago and it was just a
> > tad lower in contrast and that is all, after sitting in my cupboard 3 yr.
> >      I just got a packet of Bergger BPF 18 in the mail to test against the
> > lith film and I will report back the results.  It is a continuous tone,
> > ortho film.  I do not know the ISO of it--anyone on the list find
> > one out in
> > using this film?  John Horowy (sp) doesn't quite know either.  He
> > told me to
> > try it at a paper ISO so I will try it at 6, too, but it is
> > expensive enough
> > to not want to waste--about $2.40 an 8x10 with shipping.  Arista APH and
> > APHS are, of course, pennies a sheet. Anyone have development times and in
> > what, or any experience at all with this film?
> > Chris
> >
> >
> >
>

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Gordon J. Holtslander		Dept. of Biology
holtsg@duke.usask.ca		112 Science Place
http://duke.usask.ca/~holtsg	University of Saskatchewan
Tel (306) 966-4433		Saskatoon, Saskatchewan
Fax (306) 966-4461		Canada  S7N 5E2
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