Mamiya RB67 Film Back film use question

Discussion in 'Medium Format Cameras and Accessories' started by Pragmatist, Jul 10, 2006.

  1. Pragmatist

    Pragmatist Member

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    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???
     
  2. Marco Gilardetti

    Marco Gilardetti Member

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    Absolutely not. I do it everyday. The difference in thickness is negligible compared to backplate movement range.
     
  3. Nick Zentena

    Nick Zentena Member

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  4. kb244

    kb244 Member

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    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).

    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.
     
  5. Marco Gilardetti

    Marco Gilardetti Member

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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.
     
  6. Pragmatist

    Pragmatist Member

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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.
     
  7. Marco Gilardetti

    Marco Gilardetti Member

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    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.
     
  8. Nick Zentena

    Nick Zentena Member

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    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. Marco Gilardetti

    Marco Gilardetti Member

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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.
     
  10. kb244

    kb244 Member

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    course if it were me, I'd just have a 120 back :tongue: lol.
     
  11. Marco Gilardetti

    Marco Gilardetti Member

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    Same for me. But of course you understand that eleven years ago that-famous-auction-site was long way to come, and so was the digital thing, thus a Mamiya back was priced 1 month's salary. Nor the MAC folks were around to warn me that I was risking to destroy the whole thing and take awfully defocused pictures.

    So, I just decided by myself to give a try to the 220 back which came with the camera, and see what happened. Since then, I have even forgot that I had in mind to buy a 120 back, and spent my cash on something else.
     
  12. kb244

    kb244 Member

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    Course if i am not mistaken, now days you can get a 120 back for down to 50$ if not cheaper from keh.com , but I guess a 220 6x4.5 back makes sense if you were wanting more exposures ( tho I cant see shooting 6x4.5 on a 6x7 camera ).
     
  13. David Brown

    David Brown Subscriber

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    Funny how things like this come up. I just rec'd an RB67 kit from KEH last week. However, the back was a 220 back, even though the label on the bag it was in (and my order) was for a 120 back. I called them up and they set aside a 120 back for me to exchange.

    I don't use any 220 film, and it just seemed to me that a 120 back was the way to go. KEH offered no resistance. They didn't try to convince me that I could use 120 film in the 220 back, for instance. Of, course, I didn't expect them to, they are pretty good for customer service.:smile:

    Anyway, the timing of this thread was kind of interesting.
     
  14. kb244

    kb244 Member

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    Well funny considering I got my RB67 a lil over a month ago

    I Got the Body, 90mm f/3.8C , 180mm f/4.5, 120 back, polaroid back, prism, WLF, and overnight shipping for 310$

    I thought about a 220 6x4.5 back since it was less than 30$ , but when you got over 100 120 rolls, and only two 220s it didnt make too much sense, especially when I can borrow a 220 back from my work.