Bill, Here is a brief analysis I've done: Assuming bright open sky conditions, shooting snowy scenes call for about +2 stops from whatever the meter indicates for the snow. Using sunny/16, your exposure should be f/16 @ 1/25 secs. There are about 10 stops separating f/16 from f/500, therefore for your camera, the uncorrected exposure time should be around 40 secs (2^10 * 1/25). According to Ilford HP5 reciprocity correction, 40 sec exposure should become 200 secs exposure. But according to Polaroid.com, an exposure of 40 secs needs a correction of -2.7 f/stops for 804 film. reciprocity corrections in f/stops do not equate exactly to corrections of doublings of exposure time, but assuming they do, 40 secs should become around 260 secs (2^2.7 * 40). BTW, it is not a good idea to use reciprocity corrections charts for one film and apply them to a totally different film/technology/manufacturer.
Could you tell us what's your metered or estimated uncorrected exposure time and actual exposure times you have used? Guillermo ----- Original Message ----- From: "The Painted Horse" <paintedho...@in-tch.com> > > I could use some help here. We just got a wonderful spring time > snowfall yesterday (10") and it got me out and about with my 8x10 > pinhole camera (due to the extra light reflection of the snow). I tried > using Polaroid type 804 ASA 100 (first time using this film) and I can't > seem to get the exposures correct. The prints keep coming out real > light. Now, I could keep adjusting the time exposures but it is > expensive film and I really don't want to use the whole box of film as > testing material (that is, if I can help it). > The camera is a normal focal length (13 inches) Leonardo 8x10 and the > pinhole is F 500. Anyone out there do 8x10 pinhole Polaroids? For some > reason the time charts I use for Ilford HP5 aren't working. And yes, I > calculate for the difference in the film speeds. Any help would be > appreciated.