I have artifacts outside my 120 film frames. Why?

Discussion in 'B&W: Film, Paper, Chemistry' started by PeterB, Jul 28, 2011.

  1. PeterB

    PeterB Subscriber

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    Hi folks,

    I have run at least 8 rolls of film through my Mamiya C330 MF camera and under certain conditions (perhaps slower shutter speeds, and or over exposed images) I get artifacts outside the square frame area on the negative.

    They are different in appearance, probably unrelated. Artifact 1 is a parallel line along each of the two frame edges parallel with the film edge, darker at the top of each frame. Artifact 2 is almost like halation spilling over the top edge of the frame.

    I'm attaching two photos showing these. The 2nd attachment with orange text on it is a close-up of the 1st with the contrast increased to better show artifact 2.

    IMAG0391_HP5plus_120_image_border_artifacts.jpg IMAG0392_HP5plus_120_image_border_artifacts.jpg

    Anybody with any ideas ?

    thanks
    Peter
     
  2. zsas

    zsas Member

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    Could it be that the pressure plate is not holding the film a 100% flat and some light gets above the edges and flashes it a little?
     
  3. PeterB

    PeterB Subscriber

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    Nice idea zsas. I'll check that out in a few hours.
     
  4. markbarendt

    markbarendt Subscriber

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    I have had something similar in two cases with my RB.

    1 when it needed new foam.

    2 with my 150SF lens. In this case the effect was softer than what your examples show.
     
  5. PeterB

    PeterB Subscriber

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    Neither foam seals nor pressure plate.

    Thanks Mark. I'm unsure what to test for if the lens is faulty.

    I have replaced all foam seals surrounding the door at least 6 months ago. They are as good as new.
    I inspected the pressure plate and it appears to be working OK. Its springs compress about 1.5mm when closing the lid. There appears to be even pressure along the two outer rails. Placing ink on pressure plate and closing lid transfers ink to a piece of paper which wasn't quite wide enough so I moved it across and closed lid a 2nd time.

    see photos.

    IMAG0399_inside my Mamiya C330. outer rails higher than inner 120 film rails.jpg

    IMAG0397_pressure plate deposits ink onto outer rails.jpg
     
  6. jeffreyg

    jeffreyg Subscriber

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    Perhaps you should take a roll at only fast shutter speeds and one at only slow shutter speeds and develop both in the same tank at the same time to rule out or rule in a shutter problem.

    http://www.jeffreyglasser.com/
     
  7. PeterB

    PeterB Subscriber

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    What possible failure mechanisms of the shutter could cause the artefacts I showed in my 1st post ?
     
  8. ic-racer

    ic-racer Member

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    The image opening does not actually touch the film, the film rail does. You are seeing the effects of light get between the image opening of the camera eventually being stopped by the film rail. This is normal for that camera.
     
  9. PeterB

    PeterB Subscriber

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    ic-racer, your explanation makes perfect sense. So this is the normal behaviour for this and most likely other MF cameras?
     
  10. Gerald C Koch

    Gerald C Koch Member

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    The OP said that the artifacts are outside of each of the negative frames so it cannot be a shutter problem. I would suspect a light leak. These cameras have a removeable lens. Perhaps the lens is not making good coontact with the camera body. Since the problem is intermittent perhaps like many small light leaks it only happens in strong sunlight.
     
    Last edited by a moderator: Jul 29, 2011
  11. erikg

    erikg Member

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    This is pretty common, I've seen it before. These are internal reflections of a sort, as ic-racer said, and light piping through the film base. You notice it most in the areas with heavy exposure. Light can travel sideways through the film base, AH dyes or no, if the exposure is heavy enough. I wouldn't worry about it.
     
  12. grahamp

    grahamp Subscriber

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    You are not using 220 film with the camera on the 120 setting by any chance? The 120 setting assumes film plus backing for the pressure plate position.

    The borders showing the effect are adjacent to the film rails. The length of the effect matches the length of the frame, has a sharp boundary. I do not see any signs of a double image. If the film had moved due to the back not being fully latched (you have to press both corners of the back on a C330 to ensure full and even latching) it would have to be during exposure. And that should cause a double image.

    Low level light leak seems to be a possibility. That would imply the long edges of the back, or possibly the internal lens change baffle if the lens was removed. The shape of the fogged area suggests a uniform effect. But since the effect does not involve the edge of the film, it is unlikely to have originated anywhere except the film gate.

    If it is camera body fogging you should be able to replicate it by doing everything you would do normally, but expose the frame with a lens cap on.

    The pictures here show the film gate for a C330, which may help discussion.
    http://grahampatterson.home.comcast.net/~grahampatterson/grahamp/c330/c330.html
     
  13. PeterB

    PeterB Subscriber

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    Attached drawing shows how artefact 1 is created outside the film frame

    Thanks Gerald, if the lens board was loose the artefact #1 on each side would be diffuse, in fact they are very sharp and well defined. It is possible a light leak is contributing to artefact #2.
    erikg, I tend to agree with your analysis about the piping with intense light. That could explain artefact #2.
    Graham, no I'm using 120 film. Interestingly the pressure plate doesn't actually press tightly on the film edges, it presses on two parallel rails either side and slightly higher than the film rails - see the diagram below I drew.

    I'm now pretty convinced in the explanation(for artefact #1) offered by ic-racer whereby the light reflects off the film surface at the edges and bounces off a recess back onto the film outside the frame area - the picture shows it better.

    IMAG0403_cross section of Mamiya C330.jpg
     
  14. markbarendt

    markbarendt Subscriber

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    The 150SF is a soft focus lens, in perfect order, the aberrations are designed in.
     
  15. michaelbsc

    michaelbsc Member

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    You might try some flocking material. If there is a place you can actually put it, that is.