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/
