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  1. #11

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    hey tim

    i have heard of conversions where the camera had what looked like a funnel
    attached to the 4x5 back to choke it down to 3x4 ..
    and i was under the impression from what people who had this sort of thing done
    ( well sort of half done seeing the fellow who was doing the conversion had a massive stroke
    while the camera was apart on the bench )
    the back needed to be shimmed to keep the film to mirror distance and ground glass to mirror distance
    the same ...

    maybe they were pulling my leg, i am pretty gullible ...

    john

  2. #12

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    Umm, OK although I'm not 100% sure.. again I need to hear back from Bert (at least his advice), but, I've converted the Graflex back on my 4x5 Series D to a Graflok back using an adapter kit that Bert sent me. It's 100% reversible, and it takes less than 1 hour to do. You're taking off the Graflex mount that's attached to a rotating plate and attaching a Graflok mount. Pretty straightforward stuff.

    My guess is that it's a pretty similar situation for a 3x4 to 4x5 mod, in that the thicknesses of the 3x4 Graflex mount is probably not that different from that of a 4x5 Graflex mount, and if the rotating plate on the 3x4 is at the same or very similar distance to the film plane as is the rotatin plate on the 4x5, then it's just a matter of fitting the larger 4x5 mount on the smaller plate.

    Now, if there is a slight amount of 'shimming' that's required, well, it's an SLR, why not shim the ground glass? There's room enough in the GG mounting area for adjustments, at least the mm range.

    The only thing that a conversion is going to do is to *add* to the distance between the flange and the film plane (i.e., the modified 4x5 film plane ain't gonna get any closer to the lens; if anything, it's gonna get farther away.)

    What that means is that to achieve proper calibration in the focus, you just need to set the ground glass an appropriate distance away from the mirror. Again, such a modification would be easy (relatively speaking) and 100% reversible.

    The only non-reversible modification to my eyes with John Minnicks's conversion is the two semi-circular side notches he makes on the sides of the front to accommodate the two knobs on the front standard to allow for tilt. I think that's a fair tradeoff.

    What would you prefer? A 3x4 that doesn't get used and stays on a shelf in all it's original glory, or one that gets heavily used albeit some relatively harmless modification?

  3. #13

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    hi pablogustav

    see if you can contact the person who posted the photographs of his 3x4 to 4x5 conversion here
    http://photo.net/large-format-photography-forum/00OQrN
    he said it took him 20 mins and it was not difficult

    good luck !
    john

  4. #14

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    My guess is that the "conversion plate" mentioned in the link above comes from Bert Saunders :-)

  5. #15

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    Quote Originally Posted by rawhead View Post
    Umm, OK although I'm not 100% sure.. again I need to hear back from Bert (at least his advice), but, I've converted the Graflex back on my 4x5 Series D to a Graflok back using an adapter kit that Bert sent me. It's 100% reversible, and it takes less than 1 hour to do. You're taking off the Graflex mount that's attached to a rotating plate and attaching a Graflok mount. Pretty straightforward stuff.

    My guess is that it's a pretty similar situation for a 3x4 to 4x5 mod, in that the thicknesses of the 3x4 Graflex mount is probably not that different from that of a 4x5 Graflex mount, and if the rotating plate on the 3x4 is at the same or very similar distance to the film plane as is the rotatin plate on the 4x5, then it's just a matter of fitting the larger 4x5 mount on the smaller plate.
    It's not the thickness... it's the size. A 3x4 rb is not the same size as a 4x5. The adapter plates probably won't fit without an adapter panel of some sort. If you have an adapter panel, you have now changed the distance from the film plane to the splitter point inside the camera. Hence the focus mechanism for the 'reflex' will not focus correctly. Kinda like using Mamiya RB67 roll film backs on a 2x3 Graphics. They fit... but the focus is just off.

    tim in san jose
    Where ever you are, there you be.

  6. #16

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    Tim, there is no beamsplitter in a Graflex SLR. There's a mirror. 100%/0%. All of the light goes to the GG, or all of the light goes to the film.

    Most of the recipes for replacing a Graflex SLR's Graflex back with a Graflok back require that the ground glass be shimmed to adjust for the different flange-to-film distance.

  7. #17

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    Quote Originally Posted by k_jupiter View Post
    It's not the thickness... it's the size. A 3x4 rb is not the same size as a 4x5. The adapter plates probably won't fit without an adapter panel of some sort.
    tim in san jose
    The adapter plate IS what is provided by Bert.

    I'm attaching a couple of images from the instructions that Bert sent me when I converted the 4x5 Graflex to a Graflok back.

    Click image for larger version. 

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    This is the plate that makes the Graflex back a "Graflex". This is the part that you will remove for safekeeping. You will attach a Graflok back that you acquire yourself; Bert does not supply the Graflok back. You attach the Graflok to the conversion plate, which is the product that is provided by Bert, which in turn attaches to the rotating plate/mechanism of the R.B., seen below in front (the back plate is the plate shown above)

    Click image for larger version. 

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    The thickness of the conversion plate is made so that the film plane will be in the same exact spot as would have been the case with the original Graflex back.

    Now, my understanding is that with a 3x4 Graflex --> 4x5 Graflok conversion, it's the same exact idea, except the conversion plate has to be catered to the smaller rotating mechanism plate of the 3x4 Graflex. I'm rereading one of the Emails I got from Bert back when I purchased his kit and this is what he says:

    " You have never said if your "D" model is a 3x4 or a 4x5....need to know that, as the opening and the 14 screw circle pattern on the RB back is different for the 3x4 vrs the 4x5!"

    So I'm pretty sure it means that the configuration of the conversion plate will be different, but the basic concept and the results will be the same; you convert either a 3x4 or 4x5 Graflex to a 4x5 Graflok back, and Bert fabricates the conversion plate accordingly.

    And, to repeat, even IF some adjustments need to be made, it would only involve "shimming" the GG upwards (away from the mirror), which is, so far as camera modifications go, pretty simple and quite harmless.

  8. #18

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    Quote Originally Posted by Dan Fromm View Post
    Tim, there is no beamsplitter in a Graflex SLR. There's a mirror. 100%/0%. All of the light goes to the GG, or all of the light goes to the film.

    Most of the recipes for replacing a Graflex SLR's Graflex back with a Graflok back require that the ground glass be shimmed to adjust for the different flange-to-film distance.
    Dan,

    I know there is no beam splitter. There is a point where the image beam either goes up to the viewer or back to the film plane. That's the split point. They are tied by geometry. Change the distance to the lens for one, you need to change the other. By adding distance to the back to put an adapter on, it changes the length to the lens. The distance to the viewing screen does not change. What is in focus on the view screen, is not in focus on the film plane.

    I'm tired of trying explain it. When your pictures come out fuzzy, you know why.

    If some guy has built an adapter for the 3x4 that does not change the length from the film plane to the lens, go for it. Me? I'll just use 3x4 film or my 120 roll film adapter.

    tim
    Where ever you are, there you be.

  9. #19

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    Quote Originally Posted by k_jupiter View Post
    Dan,

    I know there is no beam splitter. There is a point where the image beam either goes up to the viewer or back to the film plane. That's the split point. They are tied by geometry. Change the distance to the lens for one, you need to change the other. By adding distance to the back to put an adapter on, it changes the length to the lens. The distance to the viewing screen does not change. What is in focus on the view screen, is not in focus on the film plane.

    I'm tired of trying explain it. When your pictures come out fuzzy, you know why.

    If some guy has built an adapter for the 3x4 that does not change the length from the film plane to the lens, go for it. Me? I'll just use 3x4 film or my 120 roll film adapter.

    tim
    i know what you mean tim
    it seems like an awful lot of work
    to ... waste 1/4 of a 4x5 sheet of film ..

    pablogustav: is the main reason why you want to convert the camera because
    your lab-guy doesn't want to scan your negatives ? using a roll back will allow you
    to shoot a larger variety of film and still remain friends with your lab guy

  10. #20

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    Quote Originally Posted by k_jupiter View Post

    I'm tired of trying explain it. When your pictures come out fuzzy, you know why.
    I'm pretty sure everybody here understands the concept. We just seem to disagree how big of a problem that is to overcome and/or the utility of doing it

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