Checking my new lightseals?

Discussion in 'Medium Format Cameras and Accessories' started by fmajor, Jan 21, 2011.

  1. fmajor

    fmajor Member

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    Hi gang -

    So i *finally* got around to putting new light seals in my RB67 Pro-S 120 magazine. The process was much more involved than my 35mm Minoltas.

    Is there any way, other than experimenting with $ (film/developing/time), to check if i did a good sealing job?

    I am concerned about how well the 4 little "patches" in the corners of the film cassette are sealed as well as the lock-up side of the cassette door (the @$$@&$ narrow little channel under the slide lock).

    Thanks!
     
  2. hpulley

    hpulley Member

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    I am about to do the same as one of my Pro-S backs has obvious leaks sometimes. On the last 3 rolls the last one was fine strangely but on the twe before that every second shot had an obvious light leak. The seals don't look good either. I got a foam kit from Nagoya, Japan and plan on redoing that back soon.

    My test will be to use a $2 expired roll of Portra 160NC and a past advertised capacity of Tetenal Press Kit chemicals to check for leaks. So it really will just be $2 and 30 minutes of my time.

    The only other test I can think of would be to cut a piece of photo paper and load it in the back somehow in the dark and close it up, expose the back to light and then develop the paper but that sounds like a more complicated test than just running film through the back.
     
  3. 23mjm

    23mjm Member

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    I just use cheap film or film I don't care about. I have some Lucky film a friend gave me and use it. You could look around on eBay and get some cheap expired stuff. The light seals are not hard to do, just a little differeent than a 35mm camera. You need to use film to check if you got it fixed right. On mine the action of winding caused the light leak, if I was careful I could keep from getting a leak. It was the way I push on the back with my thumb while winding. The new ProSD backs are the best, I have one of those and 4 ProS backs.
     
  4. hpulley

    hpulley Member

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    I still haven't figured out why my one back leaks sometimes and not other times. Doesn't matter if it is a bright sunny day, some sessions I get leaks, sometimes just one frame, sometimes every other frame. Other rolls will be perfect the entire roll. Perhaps it is during winding for me too, I don't know. I won't waste any more film through that back until I fix it.

    If this doesn't work or is too much of a PITA then I'll get a Pro SD back though they are quite a bit more expensive than the Pro S backs.

    Is the 6x8 SD rotating adapter foam free like the SD backs or does it need foam seals like the old Pro S rotating back?
    If it's foam free I want an SD 6x8 rotating adapter for sure and a power 6x8 back but the rotating adapter is expensive and rare used it seems though there are tons of the 6x8 power backs floating around which makes me wonder if they're any use.
     
  5. Ric Trexell

    Ric Trexell Member

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    I said this before but...

    The question of light seals comes up from time to time when discussing Rb's and I usually end up saying the same things but I'll also answer your question. I don't use foam, I use felt that I buy at Wal-Mart for a few cents a sheet. Foam gets gooey after awhile but felt doesn't. Wally world has it in thin sheets and I cut it with a hair cutting sissors. I buy the black. Now about your checking for light leaks, I go in a dark room and put the shutter on T, and shine a flashlight (small one) in the lense. If you let your eyes adjust to the dark room you will see the smallest light leak. Once you get that fixed you can use film but you will probably have found all the light leaks by then. Ric.
     
  6. fmajor

    fmajor Member

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    Thanks for all the replies!

    -> Ric - OK, i did something like you describe last night after the job was done: I simply took the lens off and went into a completely dark room. Then i very carefully put a small, but very bright flashlight into the camera body (after the mirror was released to the "up" position" of course).

    I saw no light leaks around the back, but wonder about the seals on the doors b/c the film is stored on the other side of the shiny, black surface the film glides along and/or the corners which are not in the immediate path of light which comes through the lens.

    Any other thoughts/possibilities?
     
  7. bdial

    bdial Subscriber

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    Assuming you have access to a darkroom and enlarging paper, cut a strip of paper that's the width of the film, thread it onto the same path the film occupies and take the camera into bright light for a while.
     
  8. fmajor

    fmajor Member

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    Hmmm, don't have any enlarging paper...

    Would un-exposed film work? I just thought about putting some 35mm film in the magazine (doing this in complete darkness).

    Would this work?!?
     
  9. Ric Trexell

    Ric Trexell Member

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    You are talking about the pressure plate I think. Well, to check that I would take out the insert and close the door, repeat the test with a light and see if any comes out through the door. Chances are if you are not seeing any light at that point you are okay to try it with film. I have not had any problems and I used it out in the brightest light. That is about the best I can think of to help you. Good luck. Ric.
     
  10. fmajor

    fmajor Member

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    Hi Ric,

    That sounds great, but i think if i take out the film cartridge, there is a huge hole, top and bottom, in the film back door assembly.
    The film cartridge is integral to sealing the entire film back assembly and the pressure plate is integrally part of the film cartidge...
     
  11. Ric Trexell

    Ric Trexell Member

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    Wow! How did I forget that little detail. I'm embarrassed and stand corrected. Ric.