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. :confused:

[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?

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

[Arne Croell]

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?

For all Apo-Lanthars I know, including the 15cm, the back cell is not tapering down towards the thread, they are straight cylinders. This looks much more like the back group of an older Symmar. Also, the back cell is just one cemented group, there is nothing to clean inside, as there is no "inside". The common separation issue of Apo-Lanthars usually affects the front cell, not the back. My assumption would be that somebody switched the back cell to a plasmat one like the Symmar, which could exhibit haze.

[nevin]

Thanks Arne!