Fungi and lenses - a recurrent topic

Discussion in 'Camera Building, Repairs & Modification' started by BlueWind, Jun 30, 2008.

  1. BlueWind

    BlueWind Member

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    Hello
    I have a Pentacon auto lens with the front (coated) element infected by fungi. Some fungi and dust also in the inner elements. The cost of a professional cleaning exceeds the price of the lens, so I may give it a try myself before considering throwig it away. Two questions:
    1- If I suceed in removing the fungus from the coated surface of the front glass, some damage to the coating will remain, caused either by the fungus and/or by my cleaning. How far will this damage influence the quality of the photos? Only in what concerns light flare? Or otherwise ?
    2- Do the inner elements have any kind of coating or other layers that may also be spoiled by fungi - or by their removal?
    Thank you in advance for any input
    Joao
     
  2. Dan Fromm

    Dan Fromm Member

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    Joao,

    There have been many discussions about the effects of coating damage, in particular on the front element's front surface, on image quality. It isn't clear that there's a strong consensus. IMO it is an empirical question, i.e., ask the lens, not strangers.

    The general rule is that if any surface is coated, all surfaces are coated.

    Good luck, have fun,

    Dan
     
  3. BlueWind

    BlueWind Member

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    Thank you
    I was just looking for what I should expect as a result. Anyway I will clean it as carefully as I can, and I will see what happens
    Regards
    Joao
     
  4. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    When you disassemble the lens, mark the edge of each element and the lens barrel so that when you put them back together, the elements will be rotated the same way.
     
  5. Greg_E

    Greg_E Member

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    If the spots where the coating is gone cause a problem, you may be able to remove all of the coating with acetic acid. There may be some issues with flouride elements so you may want to research this before soaking elements made from that type of glass.
     
  6. Dan Fromm

    Dan Fromm Member

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    Greg, are you sure that acetic acid dissolves magnesium fluoride? I doubt that it does.
     
  7. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    Are there fluorite or other exotic glass elements in any Pentacon lenses?
     
  8. Greg_E

    Greg_E Member

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    That is listed to remove several of the AR sol-gel coatings, so it may only apply to sol-gel and not sputter coated. Said to work much more slowly than hydrochloric, so if you have it, I guess you should use it? I have not tested the acetic acid yet as I got side tracked for far too long on that project, but from chemistry class, magnesium should react nicely with just about any acid. And the flourite ion should be pretty active too. Or maybe I'm remember what I read incorrectly as it has been about 2 years since I was researching this trying to find a way that I could AR coat my own lenses. Sol-gel could be done, if you could get the stuff. It is a fairly hazardous stuff with sulfuric acid as a prime "solvent" in most of these goops. This means shipping is nearly impossible.

    Don't know if there are any Penticon flourite/floride lens elements, but thought it was worth mentioning as I read this somewhere too. You end up soaking the lens in the acid until it eats away the metal. You can use a fast strong acid, or a slow weak acid from what I read. Also it was said to use strong acetic, which suggests to me way better than common vinegar (though given enough time...).