Mamiya RB 67 Bellows lens hood scale

Discussion in 'Medium Format Cameras and Accessories' started by Ross Chambers, Nov 14, 2010.

  1. Ross Chambers

    Ross Chambers Member

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    I've been using it for quite a time, but never really figured how to correctly use the scale on the horizontal rod. It reads, as you will know:

    90 127 180
    360
    110 140 250

    Does this mean that lenses of 90-110 mm focal length require setting the white indicator dot at that point? And similarly 127-140 mm and 180-250 mm?

    It does sound a dumb question, but i tried to figure it by looking through the viewfinder and vignetting isn't so easy to spot that way.

    Thanks - Ross
     
  2. Ross Chambers

    Ross Chambers Member

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    My formatting of the scale was tangled in transmission, the 360 mark is, of course well to the east of the 180-250 one.

    Ross
     
  3. danegermouse

    danegermouse Member

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    the lines correspond with the bellows extension. at the bottom of the scale there are shaded areas: 0, +0.5, +1, +1.5 etc. this will allow you to compensate the exposure depending on the lens. because the closer the focus (the longer the bellows extension) there is more dark space between lens aperture and film that needs compensation.

    dane.
     
  4. CGW

    CGW Member

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    Think he's talking about bellows lens hood accessory, not the on-camera scale. You might check online for a manual.Perhaps the butkus site has one?
     
  5. MattKing

    MattKing Subscriber

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  6. Ross Chambers

    Ross Chambers Member

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    I did look at the PDF manual, it doesn't really elucidate on the markings on the scale.

    For a while I suspected that the duplicated numbers, one above and one below at the very same point, might be for different Mamiya models.

    Now I'm guessing that they represent a range of focal lengths of lenses e.g 90-110 mm, 127-140 mm, 180-250 mm, and in each setting vignetting is avoided for lenses of those lengths.

    From experience I know that the possibility of vignetting is not necessarily apparent in the viewfinder.

    Can anyone confirm this?

    Thanks - Ross
     
  7. fschifano

    fschifano Member

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    It says, and I quote, "The numbers on the extension scale bar represent focal length of lenses." It goes on to say, and I'm paraphrasing here, that it won't vignette if you set the bellows to match the lens focal length; but it will if you extend it out too far. It's an adjustable bellows shade. How hard is it to figure this one out? I could hand this to a reasonably curious and intelligent 10 year old and he'd have it figured out in 5 minutes.
     
  8. MattKing

    MattKing Subscriber

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    I expect that the difficulty here is that OP's bellows has more focal length numbers on it than are shown in the butkus manual.
     
  9. Ross Chambers

    Ross Chambers Member

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    Thanks Matt, that is indeed the case, as I said "the duplicated numbers, one above and one below at the very same point," being "90-110 mm, 127-140 mm, 180-250 mm".

    I did find the PDF manual and read it before posting my original question, it did not say anything about this double set of focal lengths, that's why I had hoped to find experienced advice from this forum.

    To be frank, I guess that I'll just have to ask a passing 10 year old, he or she may have a polite and comprehending answer.

    Regards - Ross