Two construction details...

Discussion in 'Camera Building, Repairs & Modification' started by wirehead, May 11, 2006.

  1. wirehead

    wirehead Member

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    I'm toying with building my own medium format camera. It would be designed to shoot long exposure shots, so I don't actually need a very good shutter with it. And since there's no way I can do stuff quickly, I'm figuring that I can just make it simple with no mechanical or electronic automation.

    A lot of it can be forced to work with sufficent amounts of duct tape, no? A camera's just a light tight box with a lens on one side.

    First, what do I do about a pressure plate and film feed mechanism? Is this something I can build myself, or is it best to hack up an existing camera to make it? My mental picture is to put the spools recessed behind the pressure plate such that the film is forced between the pressure plate and some rails on top and bottom. To feed on one side, I guess I can use a one-way ratchet, but how much tension do I need to keep on the other side to have a flat film plane?

    Second, focusing mechanisms... I'm figuring that my lens options are to scrounge either medium format or large format lenses and mount them against a lens board. If I use a medium format lens, most of 'em have a focusing helical that I can use, so I can scale focus off of another camera as long as I get the correct registration distance. But if I use a large format lens, what do I do? Is it possible to derive from an arbitrary lens what the focusing scale would be based on known paramaters? How hard would it be to make the necessary light seals so that I could use it as a view camera without getting light leaks?
     
  2. Nathan Smith

    Nathan Smith Member

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    Haven't done either of these myself, but I've seen a lot of articles about both of your questions around on the web. One good place to search the archives of would be the cameramakers group. I'm pretty sure I've seen something like this a few times there over the last few years.

    Nathan
     
  3. tpersin

    tpersin Member

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  4. Frank R

    Frank R Subscriber

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    I was recently toying with the same idea. I was going to buy an old 120 box camera like a old Brownie ($10 at an antique shop) and replace the lens with a spare 90mm large format lens I have. I would mount it so that it was a fixed focus lens. I would recommend using an old box camera to save the trouble of building the film holding mechanism.

    The way to establish focus would be to use frosted Scotch tape as a temporary ground glass over the the film opening. Move the lens in and out until it is in focus at infinity and mount the lens there; use shims as necessary.

    Another way is to simply buy an old folding 120 rollfilm camera. They made lots of them and they can be very inexpensive. To avoid the problems of buying one with a sticky shutter or leaky bellows you can always buy one that is already CLAd from certosix.com.
     
  5. Hamster

    Hamster Member

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    Perhaps a cheap and more off the shelf approach would be to purchase a "old style (not NT)" Kiev 88 back together with a ground glass screen back, this way you save a lot of hassel and can concentrate more on designing the camera body. This would also give you the opition of polaroid back as well as using multiple film and ground glass.

    I am quoted ~USD 12 for a used back at my lock brick and mortar camera dealer. This would be cheaper than purchasing a cheap folder.

    The old style back gives you a peep hole on the back as well as manuel advance and frame counter. Linkage to camera body is two hooks at the bottom and a catch on the top.

    There is a page with loading instruction on the Kievholic Klub page, that should give you some ideas of the possibilies available.

    http://kievaholic.com/filmloading_oldstyle.html
     
  6. wirehead

    wirehead Member

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    Hm. certosix.com doesn't go anywhere. I might just want to pick up a folding camera and use it as-is, tho.

    The problem with the 88 back is that's a 6x6 back, and I was thinking of 6x7 or 6x9. OTOH, if it is that cheap, it might be worth messing with for a *variety* of things other than the intended purpose.
     
  7. Frank R

    Frank R Subscriber

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