I just received a supposedly "mint" Nikkor 28mm f2.8 AIS lens from Japan. It sure does look unused, but when inspecting the rear element I found this stuff:

enter image description here

The smaller spot near the top looks like it's just beneath the outer glass, while the bigger "spot" (it's actually two spots) looks like it's deeper in. And yes, I did try cleaning it, but to no avail. It's clearly not just smudges on the surface.

It's not really visible while doing the LED-test, but outdoors lighting makes it very visible from the right angle as seen on the photo.

What do you think it is?

Cheers, Vincent

  • Google "Schneideritis" -- it's not just limited to Schneider lenses.
    – Zeiss Ikon
    Jul 28, 2021 at 12:39
  • 1
    I googled "Schneideritis" and it does not look like that. My problem looks like it's between the glass elements. But thanks anyway! Jul 28, 2021 at 13:01
  • Schneideritis is a form of element separation, which is what you have -- the cemented elements are coming apart.
    – Zeiss Ikon
    Jul 28, 2021 at 13:35
  • 1
    Was it only “Mint”? Or was it “Mint [+++++]?” Jul 28, 2021 at 20:17
  • 1
    [MINT in BOX] to be precise ;) Jul 29, 2021 at 15:18

1 Answer 1


My problem looks like it's between the glass elements.

When the cement between lens elements fails, the problem is called Balsam separation (or just separation). Canada Balsam was used as an optical cement in very old lenses, but has been long been replaced with other materials in modern lenses.

The problem is not "Schneideritis". Schneideritis looks like white dots in a black area around the edge of the glass. The problem is caused by the flaking of black paint that was used to prevent stray reflections inside the lens.

Since the defect is along the edge of the lens, it may not be visible in images taken when the lens, especially when the aperture is stopped down. However, the problem may worsen over time. The lens is definitely not mint.

Some Japanese sellers use "Mint" in listing titles with horrendous defects in the description (scratches, fungus, dents, separation, etc). So it's important to read listings carefully.

Consider contacting the seller for return. If you purchased through a site that requires sellers to pay for return shipping for defective items, make sure the seller abides by those policies. Some sellers will refuse to pay for return shipping to reduce their costs and discourage returns. If that happens, you can ask the listing site to mediate.

  • Thanks for the comment, xiota! Yeah, that was what I was thinking. The seller has accepted a return although he doesn't seem very sorry at all. He says there was no problem when he checked.... But he is willing to return me the full amount (has already returned the postage fee) after receiving it and "checking the condition". I hope he just acknowledges that he messed up. And the seller is not "mapcamera", btw. Jul 30, 2021 at 18:06
  • Yep - the classic interference rings give it away.
    – bob1
    Aug 2, 2021 at 0:47

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