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  1. #11

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    I should have said these are Mamiya RZ67 backs, not sure but pix look different than my backs.

  2. #12
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    Quote Originally Posted by markbarendt View Post
    I'm not understanding how the tape could help.

    An unmodified 220 back will hold 120 film tighter to the rails, there will be less channel float with 120.
    The risk is that it will bulge in the middle. The last thing I'd want with 120 is for the film to be closer to the lens. You can get those images where the edges of the frame are in focus but in the middle of the frame the focal point is behind the subject.

    Certainly each camera and film back represents its own unique challenges.

  3. #13

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    Quote Originally Posted by ic-racer View Post
    True that the inner pair of rails don't change position, but for the film to stay flat during the exposure the film should be lying against the pressure plate, not floating in the channel. The pressure plate is slightly farther forward (toward the lens) in most 220 film backs. A few pieces of tape on the outer rails can re-position the pressure plate farther back in some cases.
    Both will guarantee flatness. Pressure plate of 220 back is slightly forward but will be in the same position as it presses against the film rails. Only pressure and counter will be different.

  4. #14
    ic-racer's Avatar
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    Quote Originally Posted by MFstooges View Post
    Both will guarantee flatness. Pressure plate of 220 back is slightly forward but will be in the same position as it presses against the film rails. Only pressure and counter will be different.
    Maybe I don't follow you. How can it be both "slightly forward" and "in the same position" ?
    Neither guarantees flatness
    Lack of film flatness is the major limiting factor in medium format photography.

  5. #15

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    I think he means "against the film rails with greater pressure".

  6. #16
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    Quote Originally Posted by BrianShaw View Post
    I think he means "against the film rails with greater pressure".
    That is the only difference.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  7. #17

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    Quote Originally Posted by markbarendt View Post
    That is the only difference.
    And if anyone honestly, truly thinks that spring tolerances in production backs are so good that there is a measurable difference in the pressure applied to the film then I have a bridge to sell you. On a film back that is a decade or 2 old you will see more variance between 220 film backs than between a selected 120 and 220 back. Even new I doubt the difference in pressure is measurable. The only difference in a mamiya 645 120 and 220 film back is a block of metal that triggers a count to 30 in the 220 rolls. Film is registered off the front of the back so the registration distance will not change.

    Film backing paper is about 0.002 - 0.004 thou thick. Springs at the price you pay for a brand new Hassy back are not that good.

  8. #18

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    Quote Originally Posted by lensman_nh View Post
    And if anyone honestly, truly thinks that spring tolerances in production backs are so good that there is a measurable difference in the pressure applied to the film then I have a bridge to sell you.
    I'm selling the same bridge!

  9. #19

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    Quote Originally Posted by ic-racer View Post
    Maybe I don't follow you. How can it be both "slightly forward" and "in the same position" ?
    Neither guarantees flatness
    Lack of film flatness is the major limiting factor in medium format photography.
    Sorry, I was just using your words. Plate is slightly forward when not attached to camera body. When the back attached to the body then the film plane on both backs will be in the same distance from lens flange. Like I said no difference except for the more pressure that is meant to compensate zero point zero xxxwhatever milimetres.

  10. #20

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    I use a 220 film back with 120 film on my RZ67 and it's fine. I also use the 120 film back. I have never had any problems with winding, exposure, jamming. Maybe I'm just not experienced enough to notice the difference.

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