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" <b...@freesurf.ch> To: <pinhole-discussion@p at ???????> 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@p at ??????? > [mailto:pinhole-discussion-admin@p at ???????]Im Auftrag von Howard Wells > Gesendet: Mittwoch, 20. Februar 2002 16:44 > An: pinhole-discussion@p at ??????? > 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 > > _______________________________________________ > Post to the list as PLAIN TEXT only - no HTML > Pinhole-Discussion mailing list > Pinhole-Discussion@p at ??????? > unsubscribe or change your account at > http://www.???????/discussion/ > > > _______________________________________________ > Post to the list as PLAIN TEXT only - no HTML > Pinhole-Discussion mailing list > Pinhole-Discussion@p at ??????? > unsubscribe or change your account at > http://www.???????/discussion/ >
