[Lititz]

I recently purchased an inexpensive Tamron Adaptall-2 SP 60-300 manual focus lens. I'm trying to identify just what I'm seeing on the first element of the inner lens barrel (see photo below). On one side, there is an arc of small spots that looks to me much like lens bubbles. But given what's on the other side, I'm not sure. It doesn't look like the (thankfully few) examples of fungus I've seen before, nor does it look like what I saw on an old lens that had separating elements along the edges. Does anyone have any suggestions? (The spots don't seem to affect photos, at least on APS-C; haven't tried it on full frame film.) Thanks very much.

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[Lowell Goudge]

It almost looks like something took the coatings off the lens. Like an aggressive cleaner or a hot liquid. Are they on the surface or between the lens elements. I can't tell.

It also could be the beginning of separation between bonded elements. They might not impact the image at all since they are relatively small, or they could, under harsh lights leave some artifacts in the image

[Lititz]

Lowell Goudge asked: "Are they on the surface or between the lens elements."

Answer: They appear to be on or in one of the inner lens elements. That is, it's not on the front of the lens where someone easily might have done damage by cleaning.

Thanks to all for the helpful suggestions so far!

[Not a Number]

I've seen water spots that look like that on the surface of lenses. If that's all they are they should clean off easily enough. Hard to tell though from just a two dimensional image.

[marcusBMG]

that

water spots

that would be my bet - legacy of a bit of condensation.