Mamiya RB67 6x8 Power Drive to Produce 6x7 or 6x4.5

Discussion in 'Medium Format Cameras and Accessories' started by grantlyd, Nov 8, 2012.

  1. grantlyd

    grantlyd Member

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    I am waiting on my new RB67 Pro SD to arrive (the body + lens at least)--in the meantime I am trying to find the back I want.

    I want to find a 120 Pro SD back, but those seem to be hard to find at a decent price. To me it would be easier to find the SD back and never worry about replacing the foam light seals.

    I recently found a 6x8 120 Power Drive back--does anyone now if this will produce clean (no vignetting) 6x8 negatives, OR 6x7 negatives? The manual reads "You can use 6x7, 6x4.5 format, with the light baffle frame mask for 6x8 format mounted on the camera body"

    To me that says--you can use the 6x8 back, but with a 'light baffle frame mask' you can produce 6x7 or 6x4.5 negatives as well. To me, it wouldn't matter if the size was 6x8 or 6x7 as long as it didn't have vignetting or the like.

    Does anyone have experience with this?
     
  2. tkamiya

    tkamiya Member

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    I got one.

    With mine,
    In horizontal position, bottom right and bottom left corner gets slight vegnetting. All other sides are clean and sharp.
    In vertical position, all along the top edge is vegnetted a little. That side isn't clean and sharp. All other sides are fine.
    There is no way to produce anything other than 6x8.

    If you use mask (never heard of it except for the mask you'd place in the focus screen area), you should be fine. I think they are stretching a bit on this 6x8 back. It's really not 8 cm wide either. It's actually 7.55cm in horizontal and 7.5cm in vertical.

    EDIT: by the way, I do have an SD body.
     
  3. tkamiya

    tkamiya Member

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    Yesterday, KEH listed 120SD back. In about 10 minutes, it was GONE.
    If you hurry, you can get 6x4.5 back for 72 dollars.
     
  4. grantlyd

    grantlyd Member

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    It makes me wonder why they came out with the 6x8 back at all...

    Yeah I will be watching KEH...I am not interested in the 6x4.5 unfortunately--I have a Fuji rangefinder for that!
     
  5. tkamiya

    tkamiya Member

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    I called Mamiya and asked about this back. The representative said they didn't sell very many of them. Apparently, it wasn't very well received in the market place. Rumor has it Mamiya wanted to compete with Fuji that had 6x8 capability. This is more like 6x7.5. Really not worth the effort....

    I keep trying to get a working 6x7 back. The last one I got, an SD type with near mint condition had light leak. Non SD type with foam seal were a mess.
     
  6. MattKing

    MattKing Subscriber

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    The biggest advantage of the 6x8 back is that all your negatives will fit on a single Printfile sheet :smile:

    Actually, the power wind is handy, and the built-in 120/220 compatibility isn't bad either.

    And when someone refers to a 4/3 format camera, you can whip out your RB67 with this back and say (preferably with an Australian accent) "4/3 format? Now this is a 4/3 format!"
     
  7. tkamiya

    tkamiya Member

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    Every time I try a foreign accent, it sounds Asian... why is THAT?
     
  8. al5256

    al5256 Member

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    RB67 6x8 back

    Hi,
    I have 6X8 back on a RB67 ProSD. The 6X8 Back on RB67 ProSD gives a 56x76mm size negative in vertical direction and 56x73mm in horizontal direction. I get 9 frames per 120 roll. The back is only for 6X8 size; it cannot be used for 645 or 6x7. However 6x8 back can be adjusted to take 220 film. There is comparison picture with a 645 back in the link below:
    http://www.flickr.com/photos/yazici/7989897307/in/photostream
     
  9. tkamiya

    tkamiya Member

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    Hi

    Do you see the symptom I described about top edge not being crisp on vertical and vignetted corners on horizontal but long end actually a bit longer with crisp edges? I've been wondering if this is common on ProSD with 6x8 back. I can scan my film and post it if my description is confusing.
     
  10. grantlyd

    grantlyd Member

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    I read somewhere that the light baffle of the body has to have an '8' marked on it--but it is still not clear whether or not this produces crisp edges.
     
  11. tkamiya

    tkamiya Member

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    No, it doesn't apply to RB-SD. I called Mamiya and asked. Since all RB-SD are designed from start to use 6x8, none of its baffles are labeled with "8" but all are capable of 6x8.
     
  12. al5256

    al5256 Member

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    The ProSD gives crisp, well defined and sharp edges and corners on vertical orientation to form a 56x76mm negative. On horizontal (Landscape) orientation bottom corners (really the upper since it is upside down) are vignetted to give 72mm long bottom side. Other than this all sides are crisp and sharp also on horizontal orientation.
     
  13. tkamiya

    tkamiya Member

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    That's probably not a good thing....

    Here's what my neg looks like.

    Frame49 was shot in vertical orientation. As you can see, top edge isn't clean. Vertically, it measures 74.5mm
    Frame51 was shot in horizontal orientation. Vegnetting is uneven and horizontally, it measures 74mm.
     

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  14. grantlyd

    grantlyd Member

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    Thanks for posting those images tkamiya! I was patient and found a 6x7 motorized back! For some reason I would rather have the crisp edges!
     
  15. voceumana

    voceumana Member

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    There are a couple of Pro-SD backs 6x7 on ebay right now in the UK. I've had no trouble with international purchases from the UK. Buy it now for about $88 each. It I already didn't have 5 backs, I'd go for them.
     
  16. tkamiya

    tkamiya Member

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    I found something interesting while playing with my setup.

    With 6x8 back, there is a little bit of play when it's set on the revolving adapter. (when it is unsecured) It will slide just a little, about 1mm, along the track. I rotated the back to vertical position and released the back, then pushed the back UP, then secured. Because the top edge wasn't sharply defined, I knew the bottom was the problem. I then took some test shots.

    With this, in vertical orientation, all edges are sharply defined. In horizontal position, just a very little on both bottom corners are vignetted. Just VERY VERY little.

    So there is some manufacturing tolerance in play here.

    I actually ordered a second body to compare and keep as a second body. Unfortunately, this body came damaged so I neither could use it or test with it. (it went back). As far as dimension goes, it was identical to mine, except the "play" was even bigger. This confirms manufacturing tolerances is part of the issue.

    I'm not sure if this helps anyone.

    I heard from a third party, with some lens and distances, more or less vignetting can be experienced. I'm trying to get a documentation on this.