What is that thing on the glass?

Discussion in 'Adapted Lenses' started by tokayto, Sep 12, 2015.

  1. tokayto

    tokayto TalkEmount Regular

    May 25, 2014
    How can i clean it? Is that cause of the oil? Aynone?


  2. southy

    southy TalkEmount Veteran Subscribing Member

    Feb 5, 2014
    Looks to me like a coating starting to come off the glass.
    • Agree Agree x 3
    • Like Like x 1
  3. tokayto

    tokayto TalkEmount Regular

    May 25, 2014
    Is there anything i can do to get it off or clean it?
  4. Kirkp

    Kirkp TalkEmount Regular

    Nov 2, 2014
    Take a look through the lens. If these coating flaws don't cause haze or fog looking through the lens, it's probably best to leave them alone. I doubt they can be cleaned -- I think you'd need to remove the coating, which might make matters worse. Lenses can have a lot of occlusions without causing too much trouble. It's haze that can really mess things up.
    • Like Like x 1
  5. ztryfe

    ztryfe TalkEmount Veteran

    Aug 19, 2014
    I rather have coating coming out than risking scratching the back element. Another vote for leaving it be.
  6. Amin Sabet

    Amin Sabet Administrator

    Aug 6, 2011
    I would try a very light clean with Eclipse fluid on a Pec pad to see if it wipes off easily.
  7. WNG

    WNG TalkEmount Hall of Famer

    Aug 12, 2014
    Arrid Zone-A, USA
    Looks like coating separation.
    Try to clean it with an appropriate cleaning fluid and non-scratching media (lens tissue, cotton, etc.) Not familiar with the products recommended by Amin, but likely along the same guideline.

    If it's not surface contaminants, leave it be. There doesn't appear to be scratches to the glass. It may not impact the images.
    If it does affect the images, then the only recourse is to polish off the remaining coating and leave the rear surface uncoated.
  8. tokayto

    tokayto TalkEmount Regular

    May 25, 2014
    As i can see there is no effect for the image quality. I guess its better to use it lile this.
  9. HabsFan

    HabsFan TalkEmount Veteran

    Apr 10, 2013
    Ontario, CAN
    You might get some weird effects when the lens flares or in out of focus highlights. Maybe some contrast loss. This would be impossible to quantify though. If the lens shoots fine otherwise, I would not worry about it.
  10. Sympa

    Sympa TalkEmount Rookie

    Sep 19, 2015
    What whould a safe way to polish off coating?
  11. WNG

    WNG TalkEmount Hall of Famer

    Aug 12, 2014
    Arrid Zone-A, USA
    It is a labor intensive task. I use cerium oxide and a micro-fiber cloth to polish off damaged coatings and fungus etched glass damage.

    This job is only as a last resort to save a worth while lens. Without the coating, there can be a loss of contrast, or increase in flare reflection.

    That is why we recommend you first shoot numerous photos under different conditions and apertures first. Coating defects like yours may or may not show in the images. If there isn't a visible impact, leave the lens as is. Trust me.

    Once you commit to removal, you cannot turn back....it will take many hours. Cerium oxide is a glass polish to remove scratches. It's very fine.
    The stripping is slow. Applying it onto a coating will immediately scratch and haze it up. Hence making the element worse optically.
    Only recourse is to continue until you've stripped down to the raw glass beneath.
    • Informative Informative x 1
  12. Sympa

    Sympa TalkEmount Rookie

    Sep 19, 2015
    Well my lens is different. The rear element is deeply recessed and it seemed dirty and fingerprinted (which was strange, being recessed by 12 cm). Some cleaning with dry microfiber and alcohol on microfiber removed the fingerprint but the reflection of it looks blotchy, uneven. Nothing to be seen however on pictures: maybe a slight loss of contrast but nothing serious. I'll just leave it like it is. It is not the most practical lens anyway (a 500 mm f/8 Kenlock with the compact length of 42 cm).
    Last edited: Sep 24, 2015
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