Mysterious small mark on front lens element

Discussion in 'Nikon' started by robert_cooper|3, Mar 19, 2012.

  1. This is a Nikon 16mm. f/3.5 Auto Fisheye (first version). There is a very small blemish about 1.5mm across and shaped like a doughnut. I've owned this lens for about 5 years and it was like this when I got it. I don't think it's fungus but not entirely sure, the rest of the front element and internals are flawless. Any idea what this blemish is?
    It looks much worse in the photo, the mark is more opaque.
    [​IMG]
     
  2. Probably dead fungus. Did the lens move from a warm/humid climate to a cold one? How does that impact your pictures? Just curious. Can you post some samples? Thanks, Kevin
     
  3. Do you have a macro lens? I'd get super close and photograph it and then upload a picture which would let us see it in greater detail. If it's fungus, it would look like a spiderweb.
     
  4. @Kevin, I'm not sure of it's entire history but the person I bought it from lived in Boston. It doesn't appear to affect my photos, I've taken many pics with light and dark backgrounds etc. and can't find any issues with it. Here is one sample shot with this lens taken on a D300 (lens was factory Ai'd).
    [​IMG]
     
  5. Mark, The first photo was taken with a 60mm f/2.8 Micro Nikkor but I redid it and got in good and close, pic was cropped and re-sized. This shows the area better.
    [​IMG]
     
  6. Looks like dead fungus to me.... And glad to see it's not affecting your pictures. It's amazing really. We always worry about keeping lenses clean and then you have these results with a lens with a spot on it. Makes one think.
     
  7. It kind of looks like the onset of fungus. It might be worth sending it to Nikon for servicing. It's a great lens.
     
  8. Agree with Michael.... And better early than later.... that stuff can mar you glass permanently.
     
  9. Kevin,
    there's no point in worrying about small spots or scratches on the front of the lens:)
    as for the OP's lens - I know, it sounds silly, but... have you tried cleaning it? a fine microfibre cloth should do the trick. If that is fungus - it will go away, leaving (or not) a trace on the element surface. If it does not go away - then it looks like a permanent damage, but merely a cosmetic one.
     
  10. It could also be mechanical abrasion. Still not clear enough ;)
    > there's no point in worrying about small spots or scratches on the front of the lens:)
    This should not be generalized. Lenses with very short focal length and very short min working distance can be less forgiving when stopped down, for example the Nikkor 10.5 fisheye focuses mere 3 cm in front of the glass. This can be checked for example by shooting mm grid paper at close focus.
     
  11. I found out that if you really want to see how dirty a lens or a sensor is, try a long exposure shot with an ND filter... Not good if you like to think your sensor is spotless... :)
     
  12. I'm with Sem here, this looks more like a 'long-term' small point abrasion, like a 2hr jog back to the car with the cap off and meeting a rough dense thing like a battery corner.
    They look like 1000's of disconnected little scratches rather than the more web-like fungus.
    Get some tubes on that lens...... Tripod and f22 manadatory.... :)
    I'm not suggesting it, but a friend of mine with a similar abrasion mark (a cheap 50mm 1.8) painted the stuff you put on old scratched cine-film, (Sorry, don't know the name) . He let it dry overnight and then polished it with a lens cloth with a drop of eclipse. It's still there, but no longer 'caught the light' when the sun was in the view. Wish I'd taken some pix!!
     
  13. To me the close-up looks more like a spot of fungus. If it's on the inside of the lens, see if you can get somebody to clean it off. Fungi can go dormant for a long time, and the spores remain potentially active even longer.
    The old black pigment thing works with things like small scratches, but you have to use real India ink (what we used to call Higgen's Infernal (Eternal, really)) - Sharpie black is too transparent to do a good job.
     
  14. The most critical question has not been asked/answered: on what side of the first element is this aberation?
    If it's on the internal side of the 1st element it is most certainly fungus.
    Send it to Focal Point in Colorado or Precision Camera Repair (Illinois?) if it is fungus.
    You can visualize it better with a film loupe turned upside down close to your eye.
     
  15. To me.. it looks like the lens was touched by a burning cigarette ....
     
  16. Andre,
    After examining it closely with a magnifying glass it's definitely internal. The outer element is smooth and shiny in the area of question. I might send it to Nikon for cleaning, I doubt they would have a replacement element beings the lens is 35+ years old. Thanks for everyone's input.
     

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