Adding a prism to a TLR

Discussion in 'Medium Format Cameras and Accessories' started by Dan Daniel, May 30, 2010.

  1. Dan Daniel

    Dan Daniel Subscriber

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    I thought I'd put this up here for the giggle factor as much as the useful factor. This is a Yashica-Mat where I removed the top part of the finder hood, then installed a Hasselblad NC-2 prism (all of $20 on ebay).

    The base plate of the prism unscrews, and then the prism fits into the opening almost perfectly. A spacer was needed on each side of the screen to raise the prism to a height that gave focus on the screen. This turned out to be about 5mm wide by 6mm high. I used wood and 3m transfer tape to hold the spacers in place and to grab the bottom of the prism. Electrical tape was then wrapped around, as you can see.

    I wouldn't pick the camera up by the prism or hold it with this tape attachment. If I keep it, I will rebuild the attachment to make it secure.

    It actually works quite well. Makes a 'chin level' 'SLR' feel camera without the mirror slap (and with the obvious parallax error). Focus is quick and precise, although it also brings every scratch and dust speck on the screen into sharp relief.

    The biggest downside is that the prism sticks out behind the back of the camera and bumps my chest when walking if I carry it around my neck.

    This was actually inspired by someone who had a Rolleiflex on my local craigslist for months with a Hasselblad chimney finder in place of the typical waist level finder. I used this Yashica-Mat because it is my trashiest TLR; I might do a final version on a Minolta Autocord.

    [​IMG]

    Another view- http://farm5.static.flickr.com/4019/4647805494_7fc9d76a32_b.jpg
     
    Last edited by a moderator: May 30, 2010
  2. Sirius Glass

    Sirius Glass Subscriber

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    Good work.

    To correct the parallax, check out the paraminder for the Mamiya C2-C3xx. The Paraminder is mounted on a tripod head and the camera above it. When the subject is properly framed and focused the paraminder is raised exactly the center to center distance of the two lenses. This distance may be more or less than for the Yashica-Mat. You will have to figure out the proper distance to raise your camera and mark it on the Paraminder.

    Steve
     
  3. ic-racer

    ic-racer Member

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    Another thing to try is those inexpensive Kiev finders. The built in TTL meter will work through the viewing lens.
     
  4. grahamp

    grahamp Subscriber

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    The prism looks almost as big as the camera :cool: As the years pass I find I am going off prism equipped cameras in favour of ground glass direct vision (large format or WLF) and rangefinders.

    Baier Fototechnik ( http://www.baierfoto.de/mameng.html ) has been doing Kiev prism conversions for Mamiya TLRs for several years, as well as some other conversions.

    On parallax:
    The Yashicamats (and most of the similar Rollei copies) have a 45mm lens axis separation. The Mamiya C series has a 50mm separation. So it is possible to use a Paramender if you mark the column or put in a collar. The Yashicas do not have the same baseplate, so the studs that help prevent twisting on the Mamiyas won't help. I don't use a prism with a Mamiya C on a tripod unless I need the camera placed too high to use the WLF. Much easier to look down than crouch to look forward.
     
  5. Jeff Kubach

    Jeff Kubach Member

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    Looks great.

    Jeff
     
  6. benjiboy

    benjiboy Subscriber

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    A quick fix if you don't have the Mamiya Paramender is to measure the exact distance between the Yasicas lenses with a pair of dividers and make a mark on the centre column of your tripod at this distance so after focusing you can raise the camera the correct amount it is only necessary at close distances because parallax is only significant at less than ten times the focal length of the lens so for normal photography with the standard lens you should have no problem.
     
    Last edited by a moderator: May 31, 2010
  7. Dan Daniel

    Dan Daniel Subscriber

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    Thanks for the comments. On parallax, I am referring to the slight difference in framing at any distance with a TLR. In some ways, it is splitting hairs, but sometimes hairs can be important to me. If you've used a 4x5, you might know the pleasure of seeing exactly what will be on the negative when checking the ground glass. So when I mentioned parallax, I meant something simple like in the following shot, the position of the top of the pole in relation to the background. 45mm may seem like nothing, but it actually does make a difference. And the only answer is an SLR or view camera, or the Paramender people mentioned. Since I am hand-holding a TLR almost always, I will have to live with the slop factor, prism or not...
    [​IMG]
     
  8. benjiboy

    benjiboy Subscriber

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    Dan, before you dismiss it try it because even with a M/F SLR you don't get 100% of what you see in the viewfinder on the film, there's usually a small percentage allowance in the periphery of the frame to allow if you are shooting slides for the mount.
     
  9. paul ron

    paul ron Member

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    What a great use of junker prisms and these days they are a dime a dozzen.

    Thanks