Re: [pinhole-discussion] Re: [pinhole-discussion]35 mm pinhole
Richard Heather wrote: Try a Blank frame with the camera in the sunlight to rule out light leaks. Richard Heather Done that, thanks. As I just reported, rather shamedfacedly, I think it's the shutter. Thanks for ideas, Katharine
Re: [pinhole-discussion] Re: [pinhole-discussion]35 mm pinhole
Try a Blank frame with the camera in the sunlight to rule out light leaks. Richard Heather Katharine Thayer wrote: 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 ___ Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.p at ???/discussion/
Re: [pinhole-discussion] Re: [pinhole-discussion]35 mm pinhole
Chris Peregoy wrote: If it seems to be no rhyme or reason then I would look to possible other mishaps. Film will respond to light in a consistent manner. One would think. Is there a problem with your Minolta shutter? Could there be a light leak in you gaffer tape tube. Or is there light reflecting off the inside of the tube. As a matter of fact I had just come back to the computer to report that I think I've figured it out. After I wrote and sent the sentence about no logical function between exposure times and negative density, it occurred to me that that sounds like a shutter malfunction, because after all film does respond to light in a consistent fashion if the laws of physics are still in place. And after THAT I suddenly remembered that the reason that camera was replaced, many years ago, was because it had a bad shutter. Which just shows two things: (1) the laws of physics still rule, and (2) one doesn't do one's best thinking when racing a deadline. Thanks, Chris, for the thoughtful suggestions. Katharine
Re: [pinhole-discussion] Re: [pinhole-discussion]35 mm pinhole
If it seems to be no rhyme or reason then I would look to possible other mishaps. Film will respond to light in a consistent manner. Is there a problem with your Minolta shutter? Could there be a light leak in you gaffer tape tube. Or is there light reflecting off the inside of the tube. Katharine Thayer wrote: 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 ___ Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.p at ???/discussion/ -- Chris Peregoy | http://www.gl.umbc.edu/~peregoy | http://imda.umbc.edu/
Re: [pinhole-discussion] Re: [pinhole-discussion]35 mm pinhole
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
Re: [pinhole-discussion] Re: [pinhole-discussion]35 mm pinhole
I'm not sure why you would have an increase in grain when using your pinhole except perhaps it was due to a thin negative. This was the one that was exposed for a fraction of a second? 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. Katharine Thayer wrote: (snip) My inspection by loupe showed it was somewhat smaller than my smallest, which was a #10. For calculation purposes I estimated it at .016 (I guess that must be inches) but I have not actually measured it. All I cared at the time, in my rush to make pictures, was it was smaller than the #10, which made blurry pictures that everyone loved but couldn't be enlarged even a little bit. My film of choice for color work is Fuji Reala, ISO 100, and I stayed with this film for the pinhole work. Okay, so here's my problem: The exposures on this thing are completely wacko. I shot four or five rolls of film to try to get a bead on the exposures but never could come up with a reliable way to predict whether the exposure would be even in the ballpark, which is why I gave up on it for the moment, although I'm quite intrigued with the potential. The only image that came out exposed right at an exposure I estimated to be near the right exposure, (8 seconds under high overcast) can be seen at (I hope I've got this right): -- Chris Peregoy | http://www.gl.umbc.edu/~peregoy | http://imda.umbc.edu/
Re: [pinhole-discussion] Re: [pinhole-discussion]35 mm pinhole
Perhaps I should add a caveat that the images themselves aren't anything special, I was just pointing the camera at whatever was handy in order to shoot off rolls of exposure trials in a hurry. KT
