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  1. #1
    Pragmatist's Avatar
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    Mamiya RB67 Film Back film use question

    OK, lets say I have a 220 6x4.5cm Pro SD back. Lets say I load 120 film into it. What will happen? Will the pressure damage the film? Aside from having to click through the remaining counter shots to wind up the film onto the spool, can this be done???
    Patrick

    something witty and profound needs to be inserted here...

  2. #2
    Marco Gilardetti's Avatar
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    Quote Originally Posted by Pragmatist
    OK, lets say I have a 220 6x4.5cm Pro SD back. Lets say I load 120 film into it. What will happen? Will the pressure damage the film?
    Absolutely not. I do it everyday. The difference in thickness is negligible compared to backplate movement range.
    I know a chap who does excellent portraits. The chap is a camera.
    (Tristan Tzara, 1922)

  3. #3

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    If you go to the

    http://www.macuserforums.com/webx?14...v86.2@.ee70433

    and check the archives you'll find the question asked a few times I think. The stock answer from tech support is you're risking the back. How much extra stress you're putting on the back I don't know.

  4. #4
    kb244's Avatar
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    Quote Originally Posted by Nick Zentena
    If you go to the

    http://www.macuserforums.com/webx?14...v86.2@.ee70433

    and check the archives you'll find the question asked a few times I think. The stock answer from tech support is you're risking the back. How much extra stress you're putting on the back I don't know.
    For those of us who are lazy. This is the reply to the 120 in a 220 (since theres not a search box on that site).

    kerry: Only in an emergency should you use 120 film in a 220 back. Because of the lack of paper backing, the film plane is slightly different in a 220 back. You may cause a focus problem at wide apertures. Another problem is that you are squeezing paper and film through a space designed only for film. This causes extra stress on the advance mechanism. Also, unless you are watching the counter, you run the risk of taking pictures beyond the 10th frame, which of course is just paper at that point.
    Also as yer using the 6x4.5 version, anything past like frame 15 or 16 is just the end of the film. As said above the extra thickness 'can' stress the rolls and such, and the extra thickness changes the film plane's location to the lens ever so slightly.
    -Karl Blessing
    Karl Blessing.com
    The Bokeh
    Color Film always existed. It's just the world was always black and white till recently.

  5. #5
    Marco Gilardetti's Avatar
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    What can people say, when they want to get rid of that huge pile of unsold 120 backs, huh? :rolleyes:

    Come on.
    I know a chap who does excellent portraits. The chap is a camera.
    (Tristan Tzara, 1922)

  6. #6
    Pragmatist's Avatar
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    Thanks for the new resource. I was not aware (nor would have thought) to look at the MAC site for a user forum. Having rehabbed several backs the "wear and tear" factor makes some sense, mostly for those who are putting the back through some hard commercial use. Marco, what film do you run regularly through yours?

    My understanding is that the plate pressure is slightly greater for 220 due to the lack of an additional backing which adds thickness. Correct? As to changing the focus plane (emuslsion surface to lens) this is something that I don't believe changes irrespective of the film type.

    Here is why: the physical distance of focus convergence is not set by the pressure plate, rather by the machined surface surrounding the frame opening that the emulsion side travels over. This would be a fixed distance for either length of film, as the point of convergence to the emulsion does not change for any back or film size. The whole purpose of the pressure plate is to maintain flatness along this surface line. This is fixed by the overall engineering of the camera. Otherwise, the points of focus to the film and the GG screen would change differentially when changing backs, and there would be a focus error as the GG convergence surface height does not change when backs are changed. The pressure plate distance will change due to the additional thickness of the paper backing, but its role is simply to provide a firm, flat base that presses the emulsion side to the machined frame opening.

    My major concern was that the slightly increased pressure might cause longitudinal scratch lines on the emulsion facing. I don't plan to run any of the thicker emulsion films such as Efke or J&C through it, rather I am thinking Provia & Ektachrome. Eventually (when a deal is found) the correct 120 back will be added to the stable (preferably motorized SD), but right now, I have the 645 one for the 220 and am chomping at the bit to experiment with this format and shorter rolls of transparency.
    Patrick

    something witty and profound needs to be inserted here...

  7. #7
    Marco Gilardetti's Avatar
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    Quote Originally Posted by Pragmatist
    Marco, what film do you run regularly through yours?
    All kind of. Ilford PAN F, FP4 and HP5, Forte 100 and Kodachrome preminently. It's... mmmhh... eleven years now. As expected, I've never seen a scratch. Useless to say, the gear works like a clockwork, as the first day. Of course, as you correctly deduced, there are no focusing issues.
    I know a chap who does excellent portraits. The chap is a camera.
    (Tristan Tzara, 1922)

  8. #8

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    Quote Originally Posted by Marco Gilardetti
    What can people say, when they want to get rid of that huge pile of unsold 120 backs, huh? :rolleyes:

    Come on.
    I know lots of people aren't fans of MAC but one thing you can say about the MAC forum tech support is they don't try to sell you anything. It's not like the vast majority of people would run out to buy a new 120 back. They'd buy used.

    You'll see the tech support people giving plenty of help to people asking about used items.

    Now they do give the "safe" answer. They don't want to tell some one to risk something and then have to deal with the issues.

  9. #9
    Marco Gilardetti's Avatar
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    I thought it was pretty clear that that was a joke. Sorry if it was not so evident.

    However, since the pressure plate clearance is approximatively 0.5 centimeters while the thickness of a paper backing is in the realm of fractions of millimeters, I think it is obvious that there is no chance to do any damage. The difference is much lesser than that of the thickness of an Ilford film compared to - say - a Forte. I would say that an increase in atmospherical humidity could cause much more stiffness to the transport mechanism than the presence or absence of the paper layer.

    And the focusing issues - those are pure nonsense.
    I know a chap who does excellent portraits. The chap is a camera.
    (Tristan Tzara, 1922)

  10. #10
    kb244's Avatar
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    course if it were me, I'd just have a 120 back :P lol.
    -Karl Blessing
    Karl Blessing.com
    The Bokeh
    Color Film always existed. It's just the world was always black and white till recently.

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