Is this a separation or haze?

[nevin]

Hello everyone! I just bought a lens recently and when I tried to check the lens condition it shows a ring of white stuff in the rear element. A picture is attached here.

Is this a separation? or haze? What's the chance it can be cleaned/fixed?

Thanks a lot!

[E. von Hoegh]

Haze. If it's a Plasmat it is likely between the front element/group, and will need to be disassembled to clean.
It could also be ageing of the cement (not separation) but I doubt it.

[nevin]

Thanks. It's an apo-lanthar 15cm, which I heard is very famous for separation.

There is also a small circle of brownish thing at the bottom of the glass in the picture as well.

[E. von Hoegh]

IIRC, an Apo Lanthar has one element and one cemented pair in front, a cemented pair in back. If that's the front cell, it will likely clean up. I can't see the brownish spot well enough to tell what it is.

[Dan Fromm]

Haze, might clean up.

I have a couple of badly separated Apo-Skopars (= process Apo-Lanthars) and their separations manifest as Newton's rings.

[nevin]

IIRC, an Apo Lanthar has one element and one cemented pair in front, a cemented pair in back. If that's the front cell, it will likely clean up. I can't see the brownish spot well enough to tell what it is.

It's at the back (i.e the rear).

[E. von Hoegh]

It's at the back (i.e the rear).

Try cleaning it. It doesn't look like separation, and I could be wrong about the construction.
Try isopropyl alcohol, ammonia, etc. Just dampen the tissue with your solvent, don't risk getting it in the cell.

[nevin]

Will try. One thing that I'm not sure is, this rear element is much bigger than the other apo-lanthar 15cm I have seen. Anyone seen such size of the back group?

[Bob Salomon]

Did you put a loupe on it to make sure it isn't fungus?

[nevin]

Did you put a loupe on it to make sure it isn't fungus?

That reminds me to bring a loupe back to office tomorrow. Thanks!