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  1. #1

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    Kalart beam splitter problem :(

    Hello friends,

    today I tried to fix a deteriorated beam splitter - upper mirror in a rangefinder of my Speed Graphic. Well, I can't say I have my PhD degree in chemistry for nothing - I am quite successful at fully re-silvering the mirrors at my lab, as it was found out today, and the coating is strong and brilliant... but the half-silvered mirrors with 50% reflection are not coming out from my hands, period

    Can't understand what to do to fix the problem - can't imagine where to get the mirror of right size in Russia How do you cope with the problem, friends?

    Cheers,
    Zhenya

  2. #2

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    Zhenya, go search around on www.graflex.org

    Cheers,

    Dan

  3. #3
    medform-norm's Avatar
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    Quote Originally Posted by Dan Fromm
    Zhenya, go search around on www.graflex.org

    Cheers,

    Dan
    Zhenya, I posted something on this topic earlier here. We don't resilver beam splitters, we go for the cheap and easy solution of buying a small piece of car window foil that is semi-transparant (driver can look out, no one can look in). I am sure with all the nouveau riche driving around Moskwa in their new limousines, this stuff should be widely available where you live too. If not, I can cut of a piece of the roll we have and send it to you. You stick this foil to the beam splitter and voila, you have something that gives enough of a ghost image to help you focussing. Or is this a kind of solution that goes against the grain of your PhD-d heart?

    On an off-topic note: how much would you charge for resilvering mirrors? I bet you could make a nice bit of side-money off it. As a new APUG-service or something.....

  4. #4

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    there's a guy on ebay sells half silvered mirrors. Maybe its just the window sticker thing, I never saw one personally.

    I've heard of using a purple dye that is normally used to color microscope slides.

  5. #5
    Donald Qualls's Avatar
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    It's very difficult to make a half-silvered mirror by a chemical silvering process. You might be able to reduce the silver coating with dilute nitric acid and frequent checks; if it's still chemically clean from application, it might reduce evenly enough to be usable. Alternately, once the coating is fully dried and set, it might be possible to reduce it with optical rouge on a suitable lap (though this tends to remove the whole coating very, very quickly).

    Another possible option for a rangefinder would be to make the mirror fully silvered in narrow stripes -- you'd then line up the images the same way as with a half-silvered beam splitter, but the moving image would be brighter and fully obscuring where it existed. Vertical alignment of the RF would be more critical than with a half-silvered splitter, and masking the stripes is left as an exercise...

    Normally, however, partially reflective mirrors are made by vacuum deposition, these days most commonly with aluminum.
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

  6. #6

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    I recently bought a piece of 50% beamsplitter glass from Edmund Scientific. This is the mirror referred to in the graflex.org article.

    I hope to get a chance to cut it and replace the mirror in my Kalart rangefinder soon. I'll let you know how it goes when I do.

    Nathan

  7. #7

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    I got a couple of pieces to repair the RF on an old folding camera from The Surplus Shed . I think the postage cost more than the pieces of beam splitter.

  8. #8

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    Quote Originally Posted by P C Headland
    I got a couple of pieces to repair the RF on an old folding camera from The Surplus Shed . I think the postage cost more than the pieces of beam splitter.
    Did that work ok? The inexpensive ones I saw there were 25% transmittance and 75% reflective, I think that %50-%50 is what is generally used.

    Nathan

  9. #9
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    Edmund Scientific is the place to get the parts to it. They carry the mirror you need.
    Curt

  10. #10

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    Quote Originally Posted by nsmith01tx
    Did that work ok? The inexpensive ones I saw there were 25% transmittance and 75% reflective, I think that %50-%50 is what is generally used.

    Nathan
    If I recall correctly, I got some 50/50 and 25/75 and I think I used the 50/50.

    I did get two different colours too - a blue and a gold, and stuck with the gold. Whatever one I eventually put in, it work

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