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#1
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Film camera question
I see a lot of developed film and contact sheets at my school and every once
in a while I see a roll of negatives or a contact sheet that has a thin band of lighter tone (darker on the negatives) at the bottom of most negative frames, as if all the frames got a little overexposure only along one edge. Usually it's the bottom of the negative frame, and the lighter band is soft edged and only about1 or 2 mm thick. The surrounding negative is normal and doesn't look fogged. Could this be caused by the shutter curtains slowing down a little at the end of the travel distance thus giving that part of the film a tiny bit more light? I can't determine if these defects correspong to the direction of travel of the camera's shutter curtain, but if it was caused by an inconsistent shutter curtain speed it should show up along the edge where the shutter curtain ends at. Can anyone advise on what couyld be causing this negative defect? Thanks for any advice. |
#2
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Film camera question
Luis Ortega spake thus:
I see a lot of developed film and contact sheets at my school and every once in a while I see a roll of negatives or a contact sheet that has a thin band of lighter tone (darker on the negatives) at the bottom of most negative frames, as if all the frames got a little overexposure only along one edge. Usually it's the bottom of the negative frame, and the lighter band is soft edged and only about1 or 2 mm thick. The surrounding negative is normal and doesn't look fogged. Could this be caused by the shutter curtains slowing down a little at the end of the travel distance thus giving that part of the film a tiny bit more light? Probably not, since most focal-plane shutters travel horizontally across the frame. A few use vertical-travel curtains. I can't determine if these defects correspong to the direction of travel of the camera's shutter curtain, but if it was caused by an inconsistent shutter curtain speed it should show up along the edge where the shutter curtain ends at. Questions: does the dark band on the negatives extend over the frames? In other words, is it continuous across the strip of film, or is it only inside the frames? If continuous, it might be a light leak. If the bottoms of the frames are all evenly darker (on the negatives) but the darkness is confined to the frames, then it may be a localized overdevelopment issue, where the very bottom (or top) of the film is getting more development. (Assuming normal rollfilm tank development.) More information, please. -- I hope that in a few years it [Wikipedia] will be so bloated that it will simply disintegrate, because I can't stand the thought that this thing might someday actually be used as a serious reference source. Because in its current form, it's not to be taken seriously at all. - Horst Prillinger (see http://homepage.univie.ac.at/horst.p...06/000623.html) |
#3
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Film camera question
"Luis Ortega" wrote
[edge of film] the bottom of most negative frames ... ~1mm lighter band ... looks fogged. [why?] One cause is the edge of the film not getting developed because it is up tight against the spiral in the processing tank. The stripe is unfixed film, showing up light on the contact sheet. If the stripe is black on the negative then: With 120/220 it is normal for some light to get to the edge of the film. The fit of the film in the spool is an ooch loose, leaving a gap between the spool ends and the roll of the film - light gets in and gets to the edge of the film. If the film is really loose on the spool, Holga & Co., then the fogging can extend in quite a ways. If this is a 35mm roll then it may be because of: a leak in the cassette; film was bulk loaded and some light got at the pancake of film in the loader; mechanical stress of loading the film on the developing reel caused fogging. And sometimes 'just because'. |
#4
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Film camera question
Luis Ortega wrote: I see a lot of developed film and contact sheets at my school and every once in a while I see a roll of negatives or a contact sheet that has a thin band of lighter tone (darker on the negatives) at the bottom of most negative frames, as if all the frames got a little overexposure only along one edge. Usually it's the bottom of the negative frame, and the lighter band is soft edged and only about1 or 2 mm thick. The surrounding negative is normal and doesn't look fogged. Could this be caused by the shutter curtains slowing down a little at the end of the travel distance thus giving that part of the film a tiny bit more light? I can't determine if these defects correspong to the direction of travel of the camera's shutter curtain, but if it was caused by an inconsistent shutter curtain speed it should show up along the edge where the shutter curtain ends at. Can anyone advise on what couyld be causing this negative defect? Thanks for any advice. This could perhaps be as a result of the film wound onto the film reels for development. Are the reels plastic or stainless? The light band MAY be the result of the developer not reaching that part of the film which is resting between the external band of concentric rings on the spool. As to why this is not the case on the upper band, I don't have a clue. I have not noted this on any of my B&W film processed by me on stainless reels. David N. |
#5
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Film camera question
David Nebenzahl wrote:
Luis Ortega spake thus: I see a lot of developed film and contact sheets at my school and every once in a while I see a roll of negatives or a contact sheet that has a thin band of lighter tone (darker on the negatives) at the bottom of most negative frames, as if all the frames got a little overexposure only along one edge. Usually it's the bottom of the negative frame, and the lighter band is soft edged and only about1 or 2 mm thick. The surrounding negative is normal and doesn't look fogged. Could this be caused by the shutter curtains slowing down a little at the end of the travel distance thus giving that part of the film a tiny bit more light? Probably not, since most focal-plane shutters travel horizontally across the frame. Most modern camera manufacturers use a verticaly traveling metal focal plane shutter in their SLR and DSLR cameras. It is definitely a symptom of a sticking shutter. Don't forget that the image is _inverted_ at the film plane and the bottom of the scene is captured at the top of the film frame. A dark stripe on along the top of the negative (which is the bottom of the scene) is a symptom of a sticking shutter, it starts a bit slow (over-exposing the top edge of the film) and then runs at the correct speed across the rest of the frame. A few use vertical-travel curtains. Have a good look at any AF Nikon SLR, a Canon EOS SLR, or any of the AF Pentax SLR camera bodies, they all have a verticaly traveling metal focal plane shutter. Even the Voigtlander rangefinder series have a verticaly traveling metal shutter. The only "modern" manufacturer to use a cloth focal plane shutter is Leica and that is only in their rangefinder cameras; Leica SLR cameras use a verticaly traveling metal shutter. I can't determine if these defects correspong to the direction of travel of the camera's shutter curtain, but if it was caused by an inconsistent shutter curtain speed it should show up along the edge where the shutter curtain ends at. Questions: does the dark band on the negatives extend over the frames? In other words, is it continuous across the strip of film, or is it only inside the frames? If continuous, it might be a light leak. It could also indicate that the shutter is sticking slightly partway across the film gate, and over-exposing that area of the film. |
#6
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Film camera question
Thanks to all. I need to check out the various suggestion offered. To
clarify, the defect is not an undevelopment effect caused by the rails of the reels impeding the developer along the sprocket hole areas but something that is happening only inside the negative frame itself. It is very evident on a contact sheet when you can see all of the frames side by side. Each contact frame appears a little whiter and more washed out along one edge, usually the bottom edge but sometimes the side edge. I work in a school and see dozens of cameras in the darkroom so I can't do a lot more than try to follow it up as it happens, but I am curious as to why this is happening. Thanks to all. "Luis Ortega" wrote in message ... I see a lot of developed film and contact sheets at my school and every once in a while I see a roll of negatives or a contact sheet that has a thin band of lighter tone (darker on the negatives) at the bottom of most negative frames, as if all the frames got a little overexposure only along one edge. Usually it's the bottom of the negative frame, and the lighter band is soft edged and only about1 or 2 mm thick. The surrounding negative is normal and doesn't look fogged. Could this be caused by the shutter curtains slowing down a little at the end of the travel distance thus giving that part of the film a tiny bit more light? I can't determine if these defects correspong to the direction of travel of the camera's shutter curtain, but if it was caused by an inconsistent shutter curtain speed it should show up along the edge where the shutter curtain ends at. Can anyone advise on what couyld be causing this negative defect? Thanks for any advice. |
#7
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Film camera question
Luis Ortega spake thus:
Thanks to all. I need to check out the various suggestion offered. To clarify, the defect is not an undevelopment effect caused by the rails of the reels impeding the developer along the sprocket hole areas but something that is happening only inside the negative frame itself. It is very evident on a contact sheet when you can see all of the frames side by side. Each contact frame appears a little whiter and more washed out along one edge, usually the bottom edge but sometimes the side edge. I work in a school and see dozens of cameras in the darkroom so I can't do a lot more than try to follow it up as it happens, but I am curious as to why this is happening. Thanks to all. "Luis Ortega" wrote in message ... I see a lot of developed film and contact sheets at my school and every once in a while I see a roll of negatives or a contact sheet that has a thin band of lighter tone (darker on the negatives) at the bottom of most negative frames, as if all the frames got a little overexposure only along one edge. Usually it's the bottom of the negative frame, and the lighter band is soft edged and only about1 or 2 mm thick. The surrounding negative is normal and doesn't look fogged. Could this be caused by the shutter curtains slowing down a little at the end of the travel distance thus giving that part of the film a tiny bit more light? I can't determine if these defects correspong to the direction of travel of the camera's shutter curtain, but if it was caused by an inconsistent shutter curtain speed it should show up along the edge where the shutter curtain ends at. Can anyone advise on what couyld be causing this negative defect? Thanks for any advice. So it's gotta be an exposure issue, and not light leaks. Most likely uneven exposure due to dragging shutter curtains, as others have suggested. A trip to the repair shop for those cameras may be in order. By the way, if the uneven exposure is along the bottom (long) edge of the frame, the offending camera has vertically-traveling curtains; along the short edge, horizontally-traveling ones. Might help to sort out which camera took which pictures. -- I hope that in a few years it [Wikipedia] will be so bloated that it will simply disintegrate, because I can't stand the thought that this thing might someday actually be used as a serious reference source. Because in its current form, it's not to be taken seriously at all. - Horst Prillinger (see http://homepage.univie.ac.at/horst.p...06/000623.html) |
#8
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Film camera question
"Luis Ortega" wrote
something that is happening only inside the negative frame itself. If this is 35mm, something everyone seems to be assuming, I'll toss my hat in with the sticky-vertical-shutter crowd. Vertical shutters were used on Exa's and Exakta 500s -- if there is one of these hanging around I'd bet money it's the one with the problem. A light leak is the usual culprit but 35mm cameras as a rule don't leak light into the mirror box. Is the film fogged or overexposed? You should only see this in contact sheets from one camera and one photographer unless the class shares common camera(s). Probably a good idea to report the problem to the camera owner/ class instructor. The problem will only get worse with time and the shutter may stop completely in cold weather. -- Nicholas O. Lindan, Cleveland, Ohio Consulting Engineer: Electronics, Photonics, Informatics. Remove blanks to reply: n o lindan at ix . netcom . com f-Stop enlarging timers: http://www.nolindan.com/da/fstop/ |
#9
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Film camera question
Nicholas O. Lindan spake thus:
"Luis Ortega" wrote something that is happening only inside the negative frame itself. If this is 35mm, something everyone seems to be assuming, I'll toss my hat in with the sticky-vertical-shutter crowd. Vertical shutters were used on Exa's and Exakta 500s -- if there is one of these hanging around I'd bet money it's the one with the problem. Oh, come on, Nicholas: how likely do you think it is that students would be using these antiquated cameras? Besides, I have an Exa, and it does indeed have a vertical shutter, but it's definitely not a focal plane shutter. It's one of the weirdest shutters I've ever seen, and even if it malfunctioned would not leave that kind of an artifact within the exposed frame. A light leak is the usual culprit but 35mm cameras as a rule don't leak light into the mirror box. Is the film fogged or overexposed? Read his post; he said the effect was within the frame only, implying no fogging outside the frame, therefore not a light leak problem. -- I hope that in a few years it [Wikipedia] will be so bloated that it will simply disintegrate, because I can't stand the thought that this thing might someday actually be used as a serious reference source. Because in its current form, it's not to be taken seriously at all. - Horst Prillinger (see http://homepage.univie.ac.at/horst.p...06/000623.html) |
#10
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Film camera question
"Luis Ortega" wrote in message ... Thanks to all. I need to check out the various suggestion offered. To clarify, the defect is not an undevelopment effect caused by the rails of the reels impeding the developer along the sprocket hole areas but something that is happening only inside the negative frame itself. It is very evident on a contact sheet when you can see all of the frames side by side. Each contact frame appears a little whiter and more washed out along one edge, usually the bottom edge but sometimes the side edge. I work in a school and see dozens of cameras in the darkroom so I can't do a lot more than try to follow it up as it happens, but I am curious as to why this is happening. Thanks to all. If the effect is inside the frame its obviously happening in the camera. Since it seems to happen on different edges in various pictures its not likely the shutter. It _might_ be an internal reflection of some sort. The way to find out is to put a small piece of ground glass in the film gate, open the shutter (T exposure) and shine a flashlight intot the lens from different angles. Actually you may be able to see a reflection just by eye. The cure is to paint whatever is causing the reflection with flat black paint or some other light absorptive material. It is possible for a focal plane shutter to cause a band of under or overexposure at one end of its travel but it will consistently at the same place on each frame. It is also possible for a focal plane shutter to cause spots or steaks on frames if it has holes in it, but this sounds like something that is not shutter related. If the camera is an SLR check for light leaks from the finder when the mirror is in the up position. Sometimes the light seals in SLR's get old and don't work. Unless you eye is pressed right against the finder some light can get in and cause some form of fogging. I am suggesting this only because your problem seems to be a little unusual and the cause may be a bit unusual. -- --- Richard Knoppow Los Angeles, CA, USA |
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