Glass/lens polishing

Discussion in 'Camera Building, Repairs & Modification' started by tjaded, Aug 9, 2011.

  1. tjaded

    tjaded Subscriber

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    Stupidest post ever? Maybe...but here goes. I have a lens, a pre-war Schneider Xenon for an exakta. The front element looks like someone used comet & a toothbrush to "clean" the front element. So my question is this: is there a good (any) place to send a lens to have the glass polished smooth? Obviously this will get rid of the coating, which is fine. It's probably not worth doing, but the lens is useless as is. I'd even try it myself if I knew what to do. At this point it would be nice to have it look decent even if it doesn't shoot well since it is a cool looking lens--and I have a few Exaktas that are display only at this point! Anyway, thoughts?

    Thanks,
    Matt
     
  2. holmburgers

    holmburgers Member

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    3M apparently makes a dry Scotch-Brite (not kidding...) glass polishing wheel for use with 1500+ RPM drills. I'd say just google around and find something that doesn't require wet stuff, and would work on such a small diameter and give it a shot. It sounds like the kind of destructive pursuit that might be a lot of fun...
     
  3. Mustafa Umut Sarac

    Mustafa Umut Sarac Member

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    Sherry Krauter is the answer may be.http://www.sherrykrauter.com/

    Your best bet is to find a broken exakta from ebay and replace the front element. I looked to bay and since I dont knowthe model , they go from 17 to 900. Be ready to pay least 250 dollars or more for repair.
    You can ask to APUG members for broken Exakta.
    Sending front element to China and ordering a new lens is another option. It might be cheaper. Search for Chinese Lens Designers at google.
     
  4. richard ide

    richard ide Member

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    Anything you do or have done to the lens will alter it's optical properties. Google "Telescope mirror grinding" or get a book on the same subject from your local library. In the final polishing stages; one makes a "pitch lap" which has the exact contour of the surface to be polished by pressing a warm mass of pitch against the lens or mirror surface. When cool you cut grooves in it and use a slurry of water and polishing abrasive such as tin oxide or cerium oxide. Using the polishing motions recommended; you will retain the same curvature of the glass and perhaps remove a couple of millionths of an inch of thickness while removing the scratches. It would be cheap to try and you have little to lose exept a few hours.
     
  5. ChuckP

    ChuckP Subscriber

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  6. steven_e007

    steven_e007 Member

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    I think any sort of pro repair is out of the question.

    Obviously it is possible to either re-polish the lens and have it re-coated, or maybe even have a new element made. You've then got to get the lens mounted , realigned and collimated.

    Possible - but bound to be far too expensive. Maybe if you want to repair something like a rare Leitz lens or a collectible Zeiss optic for your Hasselblad it might be worth looking into, I can't imagine it could possibly be worthwhile for anything like this.

    DIY options will probably leave you with a lens that is scrap - but if it is scrap anyway it might be fun trying if that is what you are into.

    Have you tried taking pictures with the lens? I bought an original German 'Geortz Dagor' that some imbecile in a shop had decided to 'renovate' with brass metal polish. He decided it was good for getting all that nasty grime off the glass, too ^_^

    The glass looks terrible - covered in scratches - but it still takes images that are remarkably sharp. Flares like mad in bright light, but if I wanted a flare free image, I'd use something else.

    If you just want a 'dummy' lens to look good on a display (perish the thought) then remove the front element, go to someone who makes spectacle lenses (many high street opticians can cut blanks to fit frames) and ask them to cut you a 1 Dioptre CR39 lens (Plastic resin) to the same diameter. Shouldn't cost much at all and will look fine...
     
  7. Greg Davis

    Greg Davis Member

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    Steve is right about an optical shop. I worked in an optical lab for a while. If you can remove the element from the barrel, they can measure the curve of the front and back sides to within a 1/4 of a diopter and use a pre-polished and coated blank (3 inch disk) of resin or polycarbonate. They then mount your lens and their blank into a machine that traces the edge of the original and cuts the blank to match. Then you remount the new lens. Glass is also an option, but more expensive.
     
  8. Ian C

    Ian C Member

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