Converting 546 film back from 120 to 200 (or vice versa)?

Discussion in 'Pentax' started by patrick_regan|1, Sep 8, 2018.

  1. Hi all,

    I stumbled upon this blog post regarding converting a 220 film back to a 120 film back (or vice versa):

    Convert Pentax 645 645n 645nii 220 film back to 120 film back – Pentax 645

    Tl;dr: there's a simple plastic part inside held on by a small screw. Flip the piece 180 degrees, and it changes the type of film the back accommodates.

    Can any of you 645 shooters attest to validity of this modification? Is it really just that simple as reversing one simple internal part? Usually when something seems to good to be true, it usually is.

  2. It could be true, you'd have to try it, if it doesn't work it's only a matter of putting it back the way it was

    I have a Bronica 645 but I have both 120 and 220 film backs

    Reversing that plastic piece on the Pentax back probably changes the position of the film plate for the different thicknesses of film, one with backing paper and one with no backing paper

    If I'm wrong about that, it may have something to do with the frame counter. However the film plate for 220 must push the film closer to the film gate since there's no backing paper on the 220, just the bare film. 120 with it's backing paper, the film plate must be further back to accommodate that backing paper. It's about keeping the film flat for both films
  3. We went through this in another thread regarding backing plates and 120/220 film. I don't think THAT makes a difference. The switchable backs for my RB don't move the pressure plate but they DO let the film advance past the 10th frame. Flipping a cam may do the same thing but you're not going to get the frame counter to go to 24 if it doesn't have 13-24 on it.

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