Mamiya 645 1000s. Light Leak or something else?

Discussion in 'Medium Format' started by peterphotography, Nov 5, 2018.

  1. Hey all,

    I've recently jumped on board the medium format train with a Mamiya 645 1000s I bought from a market? I've been absolutely loving it. I shot my first roll and came across 2 streaks which I assumed were light leaks. So 2/15 had a light leak.

    2nd roll, I decided to gaffer tape up the back of the camera to prevent any light getting through. 1/15 had a light leak.

    3rd roll, no gaffer tape on the back. Only 1 had a light leak. (Warning may be NSFW, did a shoot with a female friend of mine on the beach)

    So I'm kind of lost now in terms of how to resolve this issue. Is it a light leak, if so, why is it being so unpredictable? Are there any ways I can fix it since the gaffer approach didn't help much? Or should I just go grab a new Mamiya (this body costed me $180 AUD)
  2. It looks to me as if you might have an intermittent shutter problem.

    The picture of the lady in the bikini, in particular, looks typical of this. The rest are a bit too indistinct.

    What might be happening is that the shutter curtains might be opening as they're being 'cocked' for the next picture. At this point the mirror will be down and partly obscuring direct light from the lens - hence the dead straight cutoff of the fogging, where the shadow of the mirror falls on the film.

    It should be easy to diagnose this by opening the camera back with the filmholder removed. Use the multi-exposure lever and fire the shutter a few times to see if the curtains (stay) open as the wind-on crank is operated. They shouldn't.

    Sometimes faults like this clear themselves with use. This may be the case if the camera's lain unused for a while. Good luck!

    "Or should I just go grab a new Mamiya.."

    - Stay well away from the newer plastic-bodied M645s (Super, Pro, Pro-TL or E). They're really badly made and far more likely to be faulty, or quickly become faulty.
    andyfalsetta likes this.
  3. Just tested it! Fired the shutter 7x each for 1/1000, 1/500, 1/125 and 1/60. Curtains did not appear to stay open.

    In terms of being unused, I can't say. Owner did say it hasn't been touched for a while.

    In terms of grabbing a new Mamiya, I meant grabbing another 645 1000s! Heard about the faultiness with the newer models plus I love the aesthetic of the 645. Sorry for the misunderstanding.
  4. What Joe said and ...

    If you're using a metered prism finder, check voltage of battery

    The camera has a Moving Coil Electronic Shutter. The moving coil looks like it is a simple solenoid which is activated by a build up voltage from a condenser

    There is two separate actions associated with the electronic shutter, one the first curtain, and one for the second curtain


    The camera may need "exercising" to free things up but the PDF has precautions about releasing the shutter without film in the camera

    Use cheap B&W film for testing for a while
  5. That was quick!
    Is there any relationship between the fogged pictures. I'm thinking maybe length of time between shooting and winding on to the next frame, or time between shots? Shutter speed used? Different lens? Ambient brightness?

    It's well worth checking the condition of the body light seals. The black plastic foam does have a habit of turning to sticky goo over time.
  6. What do you mean in terms of 'exercising'?
  7. Is the light leak only in the picture area? This suggests a problem in front of the film...shutter, mirror, lens?
    Is the light leak extending beyond the picture area? This suggests a problem in the light seals at the back of the camera.
    andyfalsetta likes this.
  8. How would I be able to check? These are the scans I got from the lab and with the negatives, they seem to be contained in the picture area.
  9. Using the camera the way it is hoping all the working parts free up after the camera has been sitting around for a while without use

    Heat from your hands and from Sunlight can warm and soften grease on moving parts in the camera. The shutter curtain may have lost some of it's original flexibility and need freeing up

    Regarding light leaks from sources other than a faulty erratic shutter, I concur with Joe and Maris, check light sealing in the back of the camera, it's more likely to be that problem than a hesitating shutter curtain

    I have the same problem with one of my Mamiya Press cameras that has the adapter for removable Graflex film backs. I bought an old Graflex back and tried it out. This is what I got, but not all shots were affected, and unlike your 645, the Press has a leaf shutter in the lens

    light leak copy.jpg

    A previous owner of this Graflex back had glued some felt on the front of the film back as a light seal, but that altered the position of the film plane, so I removed the felt and tried the back without any alterations. Obviously it needs reconditioning and tried again. They are scarce, one with plastic film advance handle, a back I wish to keep using

    Light leaks can be intense or gradual. A wide gap produces intense light leakage, a small gap produces noticeable leakage over time, this is bad for films sitting in the camera for extended periods while the camera is in daylight or in room light, the camera really should be covered up while it's sitting around with a film in it. I've found light leaks so small, it took sitting in a dark room for no less than 10 minutes before I could see them, and of course shining torch light right inside the camera, sometimes on the outside of the camera, and just waiting until my eyes adjusted sufficiently to see them
    peterphotography likes this.
  10. I've tried gaffer taping the back of the camera (2 layers of black tape) and still had light leaks with my 2nd roll. Also attached are the photos of the light sealing. They seem okay? Should I still get them replaced just in case?


  11. Your seals look a bit rough, but what you get on eBay for a 1000s are just as rough. They are made from open cell sponge like you've already got in your camera. Closed cell sponge would be better. It comes in sheets of various thicknesses that you can cut strips from


    Before you re-seal it, you can place a miniature LED torch, switched on, in the where the film goes and close the door. Take the camera into a dark room at night and check for leaks. You might also be able to place the torch in the camera body if you have mirror lock up, and refit the lens

    I took a quick photo of my torch to show how small and how bright the torch needs to be
    Miniture torch.jpg

    The seal near the door hinge should be felt if I'm not mistaken, certainly not open cell sponge. But not any old felt, it should be proper camera lid felt, the right thickness and wide enough (5mm) to cover that whole surface where that scraggy bit of sponge is residing now. It's important to seal the hinge with care

    See how you go with it
    Last edited: Nov 6, 2018
  12. - I re-sealed all my old Mamys some time ago. I used high-density Neoprene foam for the narrow channels, and a strip of black velvet material for the lower door seal. I've had no sign of a light leak or any degradation of the seals since. The velvet used was a Nylon or Polyester material with a dense 'plush'.

    WRT the OP's particular leak: I've just remembered there's another light seal hidden away in the camera that might be responsible.

    The hinge of the mirror is light-sealed by a flimsy strip of black fabric. If this is torn or folded back, then light can enter the camera via the viewing screen during exposure. So I strongly recommend checking the condition and position of that fabric strip. It should overlap the mirror slightly, not be folded behind it.

    A mirror-hinge leak is usually only seen if the open waist-level finder is used though. A prism-finder may conceal the problem.

    P.S. The worst and most tedious part of replacing the foam seals is removing the old gooey ones. I found that blunted wooden tooth picks shaped to fit the groove were a good tool for the job. Together with copious amounts of tissue soaked in methylated spirit. The grooves were given a final clean with spirit-soaked cotton buds before fitting the new seals.
    Last edited: Nov 7, 2018

  13. Thank you! I'll grab my LED torch and see if I can locate a leak. If not, I'll just go repair it :)
  14. I think you should re-seal it as well. But if you try the torch, it will help if you line the film chamber with alfoil as best you can, to maximize light reflection

    If you want to check thicknesses needed for the seals, buy a packet of playdough plasticine and set small pieces on the ridges and surfaces where the seals go, close the door then open it and carefully and peel the playdough off. You can cut the playdough in half and measure the squashed section up against a ruler. This will get very close to the desired thickness needed for the seal where the playdough was squashed. The seals should be a just a little thicker than the measured playdough

    The thickness of the seal near the door hinge needs to be right, because if it's too thick, the door, when closing, can bend or distort slightly trying to compress the seal. That bending or distortion will cause problems around the rest of the door sealing

    Remember to check the mirror seal as Joe pointed out. I checked my Bronica and it's mirror seal is the same, a piece of black fabric. Use a torch to check the condition of yours
  15. The width of light seal foam needed is all over the place on M645s. It varies from around 1.5mm at the sides of the film chamber to 2mm at the top, and maybe 2.5mm around the inside of the door.

    Best bet, as someone else suggested is to buy a sheet of 1.5 mm thick foam, and to cut strips from it as needed using a steel straight-edge and a craft knife.

    I stuck double-sided tape to one side of the foam before cutting it. That way I could 'just' push the foam into the camera channels. I say 'just' because foam that thin has a tendency to twist over at random. So good luck with finding and fixing the leak.

    P.S. I still think you ought to double check the shutter blinds. They only exclude light by overlapping, and if one of the metal edge-stiffening strips has got bent, then you'll have a gap that can let light onto the film as the shutter is re-tensioned for firing.
  16. I'll give it a try. I'm gonna look for a thick foam from a hardware store. I'm still confused in that sense as I've gaffer taped/sealed the back and all hinges when I tried it with roll #2, and I still got the same amount of light leaks. So I'll check out the shutter blinds.
  17. - Sorry, but I doubt you'll find anything suitable in a hardware store. You need a small sheet of 1mm thick, black Neoprene closed-cell foam, which is quite a specialist material.

    All you're likely to find in a hardware store is upholstery foam or draught-excluder strip. Neither of which are going to be easy to cut to size, long-lasting or able to exclude light satisfactorily.

    Your best bet is an online supplier. Having said that, I know that some hobby/craft stores stock self adhesive black foam sheets. However, I have no idea what material is used or how durable it might turn out to be. Neoprene is the gold standard IME.
    Last edited: Nov 9, 2018
  18. Thank you! If only I lived in US, would've been so much easier to find the parts and repairs :/
  19. Maybe this response has been overlooked? Your testing with gaffer tape indicates the light band occurs regardless of the shut lines being covered with tape, and this additional information about the light band only being within the frame seems to support that you don't have a light seal problem at the film back doesn't it?

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