Re: Re: Reciprocity Failure with Paper Negatives

Thanks for the detailed information, but my experience has been somewhat
different, albeit with Kodak paper. I just switched to Ilford and I think
you're more right there. I need an hour exposure of the Ilford to get the
same density as a twenty minute exposure with Polymax of the same scene and
same lighting. I mean to try the comparison with an enlarger as well. Maybe
its just intrinsic speed diference between the two papers.
----- Original Message -----
From: HypoBob <hypobob@pacbell.net>
To: <pinhole-discussion@pinhole.com>
Sent: Thursday, December 07, 2000 12:25 AM
Subject: [pinhole-discussion] Re: Reciprocity Failure with Paper Negatives

> >
>
> William,
>
> Since photograpic paper is designed for the longer exposures common for
enlargers, its
> reciprocity departure is not as severe as that for photographic film, but
it is present and does
> need to be factored into the exposure.
>
> Most black and white papers seem to have a "speed" equivalent to about ISO
6. Starting with
> some figures in Jim Shull's book "The Hole Thing" and adding some other
data points and my own
> experience, I have come up with the following set of values:
>
> Indicated Reciprocity
> Exp. Time Corrected
> 15 secs 30 secs
> 45 secs 2 mins
> 1 min 2 min 45 secs
> 2 min 6 min
> 3 min 11 min
> 4 min 15 min 30 secs
> 5 min 20 mins
> 10 min 50 mins
> 20 min 2 hours
> 40 min 5 hrs 20 mins
>
> (These numbers line up on my screen, but e-mail may jostle them
significantly.)
>
> Check George L. Smyth's site -- the article by Penate. Also look at the
'airtime' site in the
> UK. (Don't have the URL right now, just a note penciled onto my graph.)
>
> My current f/360 pinhole needs 4 minutes with Ilford MGIV on a sunny day.
If you start at 1/6
> second at f/16 and work your way up to f/360, you will arrive at an
indicated time of about 76
> seconds. Reciprocity then takes it up to nearly 4 minutes. Adding a
yellow filter pushes the
> time up to 10 to 11 minutes.
>
> As usual, your mileage may vary, but half the fun of pinholing is in the
experimentation.
>
> Bob
> San Jose, CA
>
> > --__--__--
> >
> > Message: 1
> > From: "William Erickson" <erickson@ic.mankato.mn.us>
> > To: "pinhole Discussion" <pinhole-discussion@pinhole.com>
> > Date: Mon, 4 Dec 2000 13:47:33 -0600
> > Subject: [pinhole-discussion] reciprocity failure with paper negaties.
> > Reply-To: pinhole-discussion@pinhole.com
> >
> > I've been doing some multiple hour exposures on kodak polymax paper and
I
> > got to wondering at what length of exposure with a paper negative do you
> > need to begin to factor in reciprocity failure. My results suggest that
the
> > answer may be around 1 hour. Any ideas?
>
>
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Received on Thu Dec 7 06:49:44 2000