Strange light leaks on Film

Discussion in 'Medium Format' started by canwewin, Feb 18, 2014.

  1. Hi,
    I own a Mamiya 645 Super.
    Yesterday I shot and developed 2 rolls of Tri-X.
    I found those strange marks on negatives. They look like light leaks.
    The last time I used the camera (same back) about a month ago, there was no problem at all.
    Is it possible that those patterns are caused by light leaks during developing (I develop my own films) or bad loading of film in the camera?

    Thank you in advance
    L.
    00cOYp-545629584.jpg
     
  2. This is the 4th frame of the roll, 3rd is clean without patterns
    00cOYq-545629684.jpg
     
  3. Frankly, I've never had light leak problems with Mamiya 645 backs due largely to their design with no foam seals. Only a guess but I'm thinking it's not the back. Was the film fresh?
     
  4. Thank you for the reply.
    The film is fresh, but was shipped from
    Thailand. I bought it on eBay a 5 rolls
    pack. It was sent but it came back to
    the seller, and was sent again. Maybe
    those patterns are caused by x-rays,
    just a guess....could it be?
     
  5. Do the marks go outside the frame? If they don't it's not the X-rays.
    They look like light leaks to me. If they are confined to the frame, then the light came in through the film gate.
     
  6. There are some weird black line in the blank space between the frames.
    As I mentioned in my first post, the camera was working flawlessly the last time I used.
    I'll do another test roll, but with a different film....
     
  7. I had a RB67 Pro about 20 years ago. It had a flare start at about the same point as your pictures.
    The RFH has a thin gasket where the top and bottom plates attach to the main insert that had dried out and allowed light in around the wind lever area. I doubt the design of the 645 RFH is much different.
    The leak and its pattern depends on the orientation of the camera back relative to the light source.
    Check the RFH for play between the insert and shell when closed, if none its the gasket or darkslide slot leaking the light, if it has play then its a worn latch or hinge.
     
  8. I would open the back completely and see if a piece of the spool tape came off and lodged in the camera. Happens at times, did for me when I was not super careful. Lots of luck.
    jack
     
  9. By looking closer at the back I noticed
    that there are some cracks that start
    from the screws near the top of the
    back where the darkslide is placed (the
    face that is connected to the main
    body) They spread on the side as well.
    It could be the problem. I'll post some
    pictures later.
    Thank you for the comments
     
  10. Some pictures
    00cOhq-545651584.JPG
     
  11. Another one
    00cOhr-545651684.JPG
     
  12. Last one, cracks on the right side (also present on the left side, where the darkslide slot is placed)
    00cOhs-545651784.JPG
     
  13. Ludwig,
    First of all, those are not x-ray patterns. X-rays shining onto a rolled-up film produce an S-shaped band when you flatten out the film (I have posted an example here a couple of times before).
    Your streaks are all straight lines, which means that whatever caused them happened when the film was flat, i.e. sitting in the film gate.
    That points to a light leak from either the front of the magazine or from the dark slide slot. I would suspect the latter, especially because the fine striated appearance of the streaks could correspond to variations in the amount of light coming in from top to bottom of the felt which lines the thin dark slide slot.
    I don't think those cracks are (directly) connected to your problem. They are too thin, too short, and too far from the film area. They might only be indirectly responsible if they resulted in the back not being held tightly to the camera or some such issue.
    I had a RB67 Pro about 20 years ago. It had a flare start at about the same point as your pictures. The RFH has a thin gasket where the top and bottom plates attach to the main insert that had dried out and allowed light in around the wind lever area. I doubt the design of the 645 RFH is much different.​
    The 645 and RB67 magazines are rather different. The 645 insert pops completely inside the magazine "box"; no parts of the insert are visible from the outside. They are two distinct and self-contained units. The RB67 magazine on the other hand splits into two parts, neither of which is self-contained; the insert is embedded in the main part of the magazine, which also includes the external controls for advancing the film.
     
  14. Thank you Ray for your in-depth
    explanation.
    If the problem is related to the
    darkslide would applying black tape
    over the slot before loading the film be
    a temporary solution?
    Anyway I have an extra back!

    Thank you for the advices

    L.
     
  15. Ludwig, I suppose you could tape over the slot as a temporary check or fix.
    If you were willing to sacrifice a few test frames, you could load a new film and wind it to ready the first frame, leave the side of the camera pointing towards sunlight for a set period of time (say 5 minutes), then wind on the film, shoot a dummy 1/1000 sec frame with the lens cap on (just to space out the test frames), tape over the slot, wind on again, and repeat the 5 minutes exposure to sunlight. If the second frame doesn't show streaks and the first does, then it's a worn light-trap in the slot.
    You could also try a test like this, in a darkened room. With the film insert and dark slide both removed, get a small bright torch and shine it in from the rear towards the dark slide slot. If you can see any light coming out through the slot, then sunlight at the right (wrong!) angle can also get in. Try your second back while you are at it, too.
     
  16. The dark (= exposed) lines between the frames would suggest that the light came in through the interface between back and camera. The lines are light getting past the rollers on the sides of the gate, past the side of the rollers opposite to where the film gate proper is.<br>I don't think light getting in through a dark slide slot could create such lines. So have a close look at the interface. Too much play?
     
  17. Referring to http://www.cameramanuals.org/mamiya_pdf/mamiya_m645_super.pdf page 17 (pdf 20) on the right is the Roll Film Holder. Is this what you are calling the "Back"?
    Are the pictures of the camera side of the RFH? If so the cracks are most likely the source of the light leak especially if they are visible from the inside where film insert goes. If they are on the back of the camera body where the RFH attaches they may not be the problem.
    If you have another RFH try it.
     
  18. Charles, sorry, yes it is what I call "back" (interchangeable back). Sorry for the confusion. And yes the cracks are on the Roll film holder.
    I did as Ray suggested, with the film insert and dark slide both removed, I did shine light in it in from the rear towards the dark slide slot. By looking in the dark slide slot I could see the light.
    I tried the same test with another Roll film holder and there was no light visible.

    So I guess problem solved, it's "only" the dark slide slot (I was afraid it was something related to the body).
    Is there an easy way to fix it (other than tape it), or I need to buy a new one?
    Anyway thank you so much everyone for the comments and advices!
     
  19. So I guess problem solved, it's "only" the dark slide slot (I was afraid it was something related to the body).​
    There may be other leaks but its the main one. The light trap is felt of velvet and unless the shell separates so that you can get to the slot you will have to experiment.
    The felt/velvet gets compressed or wears down to where it no longer seals. You could try inserting a thin piece of black velvet into the slot with some fabric glue on one side or maybe attach a piece to the inside of the darkslide opening. Pulling the darkslide out just enough to clear the film plane may work also.
    I would seal the cracks with black silicone rubber.
     
  20. Look around for a Mamiya 645 back with a 220 insert. These usually go for considerably less $ than ones with a 120 insert. Pick up a separate 120m insert or junk the leaky one.. This might be the easiest way to get a leak-free back.
     
  21. I did as Ray suggested...
    So I guess problem solved, it's "only" the dark slide slot (I was afraid it was something related to the body).​
    Glad to have helped, Ludwig.
    I have never needed to repair the felt in a dark slide slot, but Charles' and C's suggestions are good.
     

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