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Thread: Can you diagnose this patchy look of the lens?

  1. #1

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    Can you diagnose this patchy look of the lens?

    I am considering to buy a Rodenstock Eurygon 300mm 4.5 but on closer look it appears that the front glass is a bit patchy and I could not think what to make out of it. What could it be?

    Click image for larger version. 

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    I do not want to suggest something to avoid biasing your opinion.

  2. #2

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    Re: Can you diagnose this patchy look of the lens?

    Fungus

  3. #3

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    Re: Can you diagnose this patchy look of the lens?

    Quote Originally Posted by Bob Salomon View Post
    Fungus
    Should the fungus look more like a spiderwebs or this is an early stage of it? Or this is the result after cleaning?

  4. #4

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    Re: Can you diagnose this patchy look of the lens?

    It is filthy, may or may not clean up.

  5. #5
    tgtaylor's Avatar
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    Re: Can you diagnose this patchy look of the lens?

    Although I can't make-out the full extent of the glass from your photos, I would suggest that you go the a drug store and purchase a small bottle of 91% isopropyl alcohol (100% would be better but 91% is what the stores carry), and clean the lens using good lens wipes like the old Kodak wipes which don't scratch the lens and a micro cloth. It may take several applications but a couple of weeks back I cleaned a MC Hoya filter with 91% that looked far worse than your lens. Several applications using a lens cleaner sold in the camera stores didn't do a thing and actually made things worse by leaving behind a residue! The alcohol worked and is cheap - like maybe $2 or so for a 16oz bottle whereas the junk sold in the camera stores cost several dollars an ounce and doesn't work.

    Thomas

  6. #6
    Mark Sawyer's Avatar
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    Re: Can you diagnose this patchy look of the lens?

    Could be damage to the AR coating, which won't clean off but won't affect the image much, if at all.
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

  7. #7

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    Re: Can you diagnose this patchy look of the lens?

    Could be damage to the AR coating, which won't clean off but won't affect the image much, if at all.
    +1
    Your images show reflection. In actual use the lens operates in transmission. Say the AR coating is degraded and its reflection coefficient fluctuates between 0.5% and 1%; twice as much; a dramatic change. At the same time the transmission varies between 99% and 99.5%. Who cares? Plus, these patches are totally out of focus.

  8. #8

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    Re: Can you diagnose this patchy look of the lens?

    Agreed, looks like a coating issue. Should probably not affect images at all. Does not look like fungus.

  9. #9

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    Re: Can you diagnose this patchy look of the lens?

    Looks like a coating problem to me too. Such damage can cause unwanted flare and scattering. I've got a WF Ektar with a similar issue and need to shield the damaged area to avoid flare. If you do get the lens, use a good compendium or hood with it.

    Doremus

  10. #10

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    Re: Can you diagnose this patchy look of the lens?

    Thank you everyone for the valuable input. I too thought that it might be a coating issue but I have not seen one and were therefore not very confident about it.

    What can cause such issues? Could it be still caused by a fungus?

    If it is some explainable coating issue then I will be not very worried.

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