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Thread: Converting Polaroid 250 camera to 4x5

  1. #11

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    Re: Converting Polaroid 250 camera to 4x5

    Part 2:
    Remove the Range finder. It is held in place by flat head screws that can be reached by a small flat bladed screwdriver. There is one rivet that is part of the lever system that must be drilled out. A 6" long 5/16" drill makes it an easy job. Set the RF aside in a safe place.
    The now stripped frame of the camera will have a Hobby plywood frame made to take the cut film holder. Two vertical stanchions are made and glued in place along side of the vertical ridges that are case into the housing. The wood is just thick enough to bring the cut film holder frame level with the back of the camera body. It will be obvious to you when you place the wood next to the cast ridges. These stanchions will take all of the forces loading/unloading the cut film holder. Use on a quality epoxy to glue them into place. Screws are not needed. JB Quick 5 minute epoxy is ideal and super strong. Use an acid brush or the like to spread the epoxy on the wood. Use only enough to glue the wood in place. Clamp in place with enough force to hold the wood in place,not ooze out the epoxy. Lever clamps and light close-pin clamps work well. you can take the clamps off in an hour.
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    As the two stanchions are setting up now is a good time to open up the old lens mounting hole. You can use a high quality Hole saw but a Dremel tool with a sanding drum is just as easy and allows small adjustments as needed. Remember as stated to allow the room for your locking ring. Make sure you can mount the lens without damaging the bellows on the inside. Make sure you have the bellows plate screwed back onto the back of the lens plate. It is steel and cuts easier when attached to the lens plate. When grinding/sanding the hole larger just use easy circular motions. It will take about 30 minutes to do.
    The casting is thick enough you could do a surface mount or even thread the hole. The surface of the lens holder is not flat,there are raised portions than need to be ground down. Easy with the Dremel tool.
    Once you have the hole enlarged for your lens, do a trial fit. the trip lever will be on the left. Make sure you can move all the lens settings/levers.
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    You trip lever may or may not be like mine. Fuji and Nikon lenses are very easy to trip,my lens required a dog-leg tripping lever. I had to mount a wood block to allow a pivot point for the tripping lever.
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    Part 3 to follow

  2. #12

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    Re: Converting Polaroid 250 camera to 4x5

    Part 3:
    The wooden pivot block is glued in place. JB Weld is used.
    Click image for larger version. 

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    While the block is setting up the Range finder is prepared. The wood block is just thick enough to have the view port clear the wood cut film holder.
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    The range finder has three screws holding it's cover on. The two front screws must be reachable in order to do repairs if needed. The third back screw can be left off as it will be covered when glued down.
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    A trial fit is used before it is glued down.
    The Range Finder's range lever will be moved by a steel "L" bracket cut from a 22 gauge piece of scrap. The spring on the range finder is stiff. Aluminum was found to bend over time causing the range finder's zero to be lost. A common number 6 screw and nut is used in the hole drill out in a previous step. This bracket is used to fine tune the zero by bending when the camera is complete and very easy to do.
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  3. #13

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    Re: Converting Polaroid 250 camera to 4x5

    Part 4:
    Once you have glued the Range Finder in place you can now mount the cut film holder back. The two vertical stanchions are now set and will support the cut film holder ( CFH ) frame.
    The CFH is a simple three sided frame built to hold a CFH with a slight friction fit. You want the thickness of the wood to be just to clear the thickness of the CFH. Taper the loading ends of the wood to ease the CFH insertion into the frame.
    The CFH is not glued into place until you have verified coverage of the wide open lens.
    A Ground Glass holder is used with the aid of a dark cloth to adjust the holder to the dead center of the projected image of the lens.
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    This is a simple ground glass holder made from a Dollar Store plastic picture frame and "ground" using valve grinding compound" on a dead-flat surface. The frame is hobby plywoods as well. Keep screws for the glass holder below flush. Easy to do and unbreakable.
    The lens is opened up and a distance object is aimed at and the frame is zeroed. The frame is marked and then glued in place and allowed to dry. ( camera is out of focus)
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    Last edited by Rapidrob; 2-Mar-2018 at 20:49.

  4. #14

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    Re: Converting Polaroid 250 camera to 4x5

    Very interesting. Thanks!

  5. #15

    Join Date
    Jan 2015
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    61

    Re: Converting Polaroid 250 camera to 4x5

    A related question.
    Which Polaroid model is the best for a 4x5 conversion as far as coverage goes?
    Any model that cover all of the negative?

  6. #16
    Randy Moe's Avatar
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    Dec 2011
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    Re: Converting Polaroid 250 camera to 4x5

    Yes, thanks for the demo. Very cool!

    I notice that some hobby wood is just right for LF creations.

    Of course, your micrometer may vary. That's not for OP, but other inquiring minds.

  7. #17

    Join Date
    Feb 2010
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    996

    Re: Converting Polaroid 250 camera to 4x5

    They all have the same lens/bellows so all should cover 4x5 about the same (in the 100-series polaroids, which the 250 is part of)

  8. #18

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    Re: Converting Polaroid 250 camera to 4x5

    As stated above,it the back of the camera can be converted to a flat surface by wood fillers I see why none off them could not be converted.
    If the camera has the Zeiss range finder your pretty much good to go.

  9. #19

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    Re: Converting Polaroid 250 camera to 4x5

    Part 5:
    The range finder is glued into place once you have verified the lens zero. The two nubs on top of the frame provide a good lateral support of the wood block. They are spaced far enough apart for Range Finder lever adjustment. By moving your mounted RF left and right you just bring your hand made bracket to just touch the RF's actuator lever. A very little movement of the RF lever will effect the zero of the device. That being said,you made bracket mounted on the two focusing arms will be bent slightly to find the lens/ RF zero. It very east to do.
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  10. #20

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    Re: Converting Polaroid 250 camera to 4x5

    Part 6:
    Now for the hardest part. The shutter tripper. As stated above the Fuji and Nikon lenses are so east to do I'm not going into it.
    The Rodenstock lens is the exception. It has a long throw tripper and the Polaroid red shutter button has a short throw. You have to make a mechanical advantage device. I tried several shapes and materials to be used to find which worked the best.
    Things to take into consideration are:
    How far does the lens trip lever have to move?
    How far must it reset in order to re-cock the lens?
    Is there enough return spring force to allow the cameras exposure button to reset?
    While this sounds like " I can't figure it out,just forget it" it really is so easy to do if my dogs had thumbs they could do it!
    1. Rotate the lens in the front standards hole until there is enough room for the lens trip lever to move. You do not want the trip lever to go father down towards 6 o'clock than 7 o'clock. This will prevent the device you will make from going behind the lens trip lever.
    The wooden pivot block has been epoxied in place and has set up. The casting ridges will help hold it into place.
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    I'm using stiff wire to go around the shutter trip blade of the camera itself. By using a stiff wire you can "fine tune" the exact tripping point of the shutter be shortening or lengthening the throw of the wire. Very simple to do .
    Now the hard part made the simple and easy way. You need to make a dog-leg lever to move the lens trip lever. The easiest way to move a resistive object is my a wheel. This allows a constant,smooth fully controllable force. You will have tools in your possession to bend the correct radius. A wooden dowel,a drill bit 1/2" or larger, just about anything round that can take the force of you bending the dog leg lever.
    I have found Aluminum is NOT a good material to use. It does not like to be bent,adjusted and under many "trips" of the shutter it broke. You know it will fail for the best shot of your life exposure.
    I found a scrap piece of 22 gauge steel sheet. You can bend it several times and find tune the throw of the lever way before the steel shows signs of stress cracking.
    This was a concept test lever. Aluminum,it did not hold up well but got me thinking in the right direction.
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