I base my paper negative pinhole images on a EI of about 6 as this is as low as my spot meter goes. Somewhere I obtained info for reciprocity multiplication factors, thought it was at www.mrpinhole.com but can't find it. I tend to guessimate from a known (successful) exposure for that combination of f-stop/camera. In practice, with my 5x7 pinhole I usually use 1 min exposures. Couple of weeks ago I test drove my newly constructed 8x10 and due to a larger pinhole, 30secs was perfect. Here's the result http://www.photocritique.net/g/s?zzkuYc-p27143605(posted 8220 days ago)