Chris Peregoy wrote: I would try to get a > better fix on your pin hole size. I use a comparator as described in > Eric Renner's book, page 113 and 114 with the use of an enlarger to > enlarge a metric scale. Then figure for reciprocity failure. I always > try to make an accurate guess first with meter and calculations, then > after gaining experience I can usually guess without these aids. >
I've done all those things, except for precisely accurately measuring the pinhole, and even there I doubt that my estimate is all that far off. I've done pretty well with my five other pinhole cameras, estimating the pinhole size and making my way to a good guessing range for exposures, with only one or two trial exposures in each case. The point was that for this particular camera, even allowing a large margin of error on my estimation of pinhole size, the range of exposure times that would be predicted seems to be many magnitudes too long (even without figuring in reciprocity failure) compared to the empirical data. The question was, does anyone have any idea why that would be, and more to the point, why there doesn't seem to be a logical function that I can identify connecting the exposure times to how the negatives turn out. After I could see that using the textbook rules wasn't going to get me anywhere very fast, I started running exposure trials, taking the same subject at 6 or 8 widely differing exposure times, taking careful notes, but since there didn't seem to be any rhyme or reason to the results at the end of a week or so, I decided I couldn't spend any more time on it until after I get this show up. I just wondered if someone had a bright idea I hadn't thought of. My first thought was that maybe there's something squirrely about this film, but later I read in one of the books that it's considered a good film for color pinhole, so I guess it's not that. Katharine Thayer
