Kalart beam splitter problem :(

Discussion in 'Camera Building, Repairs & Modification' started by eumenius, Nov 10, 2005.

  1. eumenius

    eumenius Member

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    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 :sad:

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

    Cheers,
    Zhenya
     
  2. Dan Fromm

    Dan Fromm Member

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  3. medform-norm

    medform-norm Member

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    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. Kevin Roach

    Kevin Roach Member

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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. Donald Qualls

    Donald Qualls Member

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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... :wink:

    Normally, however, partially reflective mirrors are made by vacuum deposition, these days most commonly with aluminum.
     
  6. Nathan Smith

    Nathan Smith Member

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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. P C Headland

    P C Headland Subscriber

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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. Nathan Smith

    Nathan Smith Member

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    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. Curt

    Curt Subscriber

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    Edmund Scientific is the place to get the parts to it. They carry the mirror you need.
    Curt
     
  10. P C Headland

    P C Headland Subscriber

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    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 :smile:
     
  11. eumenius

    eumenius Member

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    Dear friends,
    first of all, thank you for your comprehensive reply! :smile: I think that the sticky tape thing won't do in my case because of my sense of beautiful - believe me, I would not be able to sleep if I know that there's a piece of tape glued over optical surface :smile: Edmund Scientific mirror, mentioned on Graflex site, sounds OK - I can cut a piece of needed dimensions, but again I'm in trouble :sad: To order it, I should transfer the money somehow to EdSci, not an easy thing. Or I should ask someone to buy it for me and to send it here, paiyng him via Western Union and losing some 20% of total price. I will try first one thing: unless I'm mistaken, one of FED rangefinders definitely contains a half-silvered beam splitter element, so if it's big enough why not ask my friend camera repairman? He would know it for sure, maybe I can get hands on one.

    As for re-silvering on order, first of all, I should master the process first - I love to do my job and be completely sure of the result, especially when it's a serious thing used by others :smile:

    Thanks again,
    Zhenya
     
  12. medform-norm

    medform-norm Member

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    Zhenya, I forgot you are a person who cares deeply about the cosmetics of your gear. Suddenly I remember some months ago you didn't want to take off the leatherette of a Voigtländer Vito to get to the shutter. Instead you wanted to tackle the problem from the inside (which seemed impossible to me). Whatever happened to your Vito project anyway?

    Recutting beam splitter glass from another camera is worth a try - but take extreme care. This is very fragile stuff and you can easily damage the layer that does the beam splitting as well as break the glass. Good luck, Norm
     
  13. eumenius

    eumenius Member

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    Hi Norm,

    yep, I really care about the cosmetics - some years of camera repair for people taught me in some ways :smile: I love clean and carefully made and repaired cameras, so a piece of tape in viewfinder scares the hell out of me :smile:

    My Vito works fine now - I had to disassemble it quite seriously, I wonder why the mechanics of it are so complicated! It's okay for Germans, too - if we take Leica's focal plane shutter... :smile: There's one big obstacle - a need of special key to unscrew the retaining ring, but I did overcome it somehow, then filed there two regular slots. Damn, I hate such land mines :smile:

    I am sure that the FED mirror should be about the right size or even a bit smaller - but I can't exclude the opportunity to ask friends to buy the glass from Edmund for me. I got a diamond pen and skilled hands, so cutting it would be not a problem for me - after all, I was cutting 18*24 cm glass photo plates for two years, making plenty of 6*9 from them for our electron microscope :smile:

    Cheers,
    Zhenya

     
  14. medform-norm

    medform-norm Member

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    well, you wouldn't actually *see* the piece of tape and it wouldn't be in the viewfinder but on the beam splitter itself. But for you, *knowing* it is in there must be hard enough. We do lots of repairs too, but mostly for functional purposes, good cosmetics are not going to make the pictures better. A very German point of view. :smile:

    Glad to hear you got the better of the Vito. Having fun with it? It's a really nice little camera. My dad had one and used it until he died in the nineties. Made some very beautiful shots with it too! Great lens, the little Skopar. How's yours?

    Regards, Norm
     
  15. eumenius

    eumenius Member

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    Thanks, Norm! The very knowledge about the tape inside will make me shudder... and I'm somehow German too, to be precise, a German Jew aus Stuttgart :smile: My ancestors left for Moscow in 1908, so it was about being between hammer and anvil :smile: I like practical approach, but the tool should be and look nice :smile:

    Vito is a real fun with its tiny Color-Scopar, and the exposure meter still works! MAybe Gossen did it for Voigthlaender?

    Cheers,
    Zhenya
     
  16. medform-norm

    medform-norm Member

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    It appears as though someone has taken my idea for repairing beam splitters to eBay to make some petty cash. Oh well, good luck to him! All that effort to make 5$. And I don't think he's going to send millions of them either.