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  1. #11

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    The only 120 cameras I have used in which I get even spacing are red window where you depend on the numbers on the backing paper, wind those on very carefully and the spacing can be very good, but with any form of auto wind it can't be done, the stop depends on the thickness of the film, so it is bound to vary, but as long as you get 8/12/15 or 16 clear frames, depending on format then don't worry, everything is as it should be.
    Richard

  2. #12

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    Re Laser's comment - I never knew this, although I guess it makes some sense. But is that the only way the the camera can meter the film advanced? How about a geared ratio of "advanced distance" related to the aperture opening size (the window at the film plane) plus some for space? Too much inconsistency due to whether the roll is tightly or loosely wound? Would be interesting to hear the original Rollei engineers' discussion on this. They would likely opt for a calculable number, even if subject to a steep variation curve.

  3. #13

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    Quote Originally Posted by George Collier View Post
    Re Laser's comment - I never knew this, although I guess it makes some sense. But is that the only way the the camera can meter the film advanced? How about a geared ratio of "advanced distance" related to the aperture opening size (the window at the film plane) plus some for space? Too much inconsistency due to whether the roll is tightly or loosely wound? Would be interesting to hear the original Rollei engineers' discussion on this. They would likely opt for a calculable number, even if subject to a steep variation curve.
    Laser is not correct in how they calculate film travel. If you look at the take-up area, you will see a fine-toothed gear on the left end of a rod. On the right end of that rod, on the other side of the wall, is a smaller gear. This gear in turn rotates yet another gear (larger) which in turn rotates a disk with slots in it. These slots are evenly spaced, and a lever will drop into the slot to stop the forward winding.

    So the 'information' imparted to the internal mechanism is based on the linear travel of the film. That first thin gear in the take-up area is spring-loaded. Push it and you will see- as the film spook diameter increases, the gear moves, but the 'information' it is transmitting remains based on the linear distance the film travels. No need for any complex curves or logarithms or algorithms, no need to worry about film thickness, etc. That is how they solved the issue: linear film motion causes specific, constant gear motion.

    So on a Rolleicord, when you rotate the wind knob, you will be directly turning the film spool itself. this, in turn, rotates the thin gear on the left side > internal gear> internal gear > slotted disk. The only difference for a Rolleiflex is that the crank handle turns a gear which truns naother gear which finally turns the gear that is the film spool drive.

  4. #14

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    I'll add links to a Rolleiflex T in pieces put on flickr by someone (not me). Although the T is different in many ways form both the ROlleicord and the Rolleiflex, the basic frame counting and winding system is the same concept. In this first photo, the two '1's point at a small gear to their left. This gear has a silver center. That is the other end of the rod that goes across the upper film chamber. So as the film moves the large gear on the left side of the film chamber, this small gear is rotated, which rotates the larger gear above it. When the back is closed, the center of that larger gear- small gear- engages the film counter dial to the right.
    http://www.flickr.com/photos/2950454...th/5042303172/

    The back of the film counter dial has another disk with notches, shown here.
    http://www.flickr.com/photos/2950454...57624987139266

  5. #15
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    Quote Originally Posted by R.Gould View Post
    The only 120 cameras I have used in which I get even spacing are red window where you depend on the numbers on the backing paper, wind those on very carefully and the spacing can be very good, but with any form of auto wind it can't be done, the stop depends on the thickness of the film, so it is bound to vary, but as long as you get 8/12/15 or 16 clear frames, depending on format then don't worry, everything is as it should be.
    Richard
    Close, but actually it uses a wheel to measure the length of film passing by very similar to the way a 35mm camera measures the film. It adjusts film spacing based on a fixed rotation of the wheel, not the diameter of the spool. Do you have good spring tension on the wheel?

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