Re: Type 55 reciprocity adjustments

My memory of my work with type 55 is that the reciprocity corrections used
for other film worked fine with type 55. I exposed for negative, not
positive, ASA 25.
----- Original Message -----
From: "Markus Birsfelder" <birs@freesurf.ch>
To: <pinhole-discussion@pinhole.com>
Sent: Wednesday, February 20, 2002 11:12 AM
Subject: AW: [pinhole-discussion] Type 55 reciprocity adjustments

> I am not sure you refer to this post, but here is what I have saved:
>
> ==================
> Guy,
>
> Back in the 1974 Jim Shull published "The Hole Thing", a pinhole
photography
> book which includes a table of
> reciprocity corrections for enlarging paper used in pinhole cameras.
> (Apparently he was using Luminos
> Industrial F which he rated at an ASA of 10.)
>
> Using Shull as a starting point and gathering a few other data points from
> web sites such as those of George
> Smyth, Airtime, and Penate and adding in my own experience, I have
> constructed a reciprocity table that works
> for orthochromatic B&W paper in pinhole cameras in sunlight:
>
> Indicated Exposure Corrected exposure
> 32 secs 1 min 15 secs
> 45 secs 1 min 50 secs
> 64 secs 3 mins
> 91 secs 4 mins 40 secs
> 128 secs 7 mins
> 181 secs 10 mins 50 secs
> 256 secs 16 mins 40 secs
> 362 secs 25 mins
> 512 secs 40 mins
> 724 secs 64 mins
> 1024 secs 104 mins
>
> Using this table, I can consistently get good shadow detail (an indication
> of proper exposure) with Agfa
> Multicontrast Premium and Ilford Multigrade IV RC papers. Although these
> papers have different published
> paper speeds, I have found that assigning them the same "daylight ASA" of
6
> works in practice.
>
> In the darkroom under enlarger light, B&W paper does not seem to exhibit
> much reciprocity departure up to
> times around two minutes. Possibly the fact that in sunshine the light
> meter is measuring a good deal of
> light to which the paper is not sensitive may account for some of the
> variation from indicated time. My
> pinhole cameras have had f/stops ranging from about 180 to about 360, so
> most of my work has been in the 4 to
> 40 minutes range.
>
> Bob
>
> p.s. I have also found that using a yellow filter on the camera with
these
> papers lowers the contrast and
> yields a paper negative that is much easier to print, but of course still
> results in that "orthochromatic
> look". The filter blocks UV and allows you to optimize the camera for the
> wave lengths to which the paper
> responds, i.e., about 500nm.
>
> ==================
> -----Ursprungliche Nachricht-----
> Von: pinhole-discussion-admin@pinhole.com
> [mailto:pinhole-discussion-admin@pinhole.com]Im Auftrag von Howard Wells
> Gesendet: Mittwoch, 20. Februar 2002 16:44
> An: pinhole-discussion@pinhole.com
> Betreff: [pinhole-discussion] Type 55 reciprocity adjustments
>
>
> Late last year a list member published a chart of reciprocity
> adjustments with Type 55 Polaroid. I printed it out, lost it, and now
> can't find it in the archives. Some interior work has taken me into
> uncharted (to me) realms with this wonderful material. Help and thanks.
> Howard Wells
>
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Received on Wed Feb 20 13:01:27 2002