Fungus?

[Sdrubansky]

It's on the outer edge between the front elements on a Sinaron SE 180mm.
Only visible with certain angles of light, looks like a cross between dust and scratch,
about 3mm long.

Any help is most welcome.
M

[Steve Hamley]

Doesn't look like separation to me. Usually separation shows multicolored areas.

Cheers, Steve

[Steve M Hostetter]

This isn't fungus this is on the surface of the lens it would appear ... Looks like the lens cap came off in the bag and rubbed the glass element..

[Sdrubansky]

This isn't fungus this is on the surface of the lens it would appear ... Looks like the lens cap came off in the bag and rubbed the glass element..

It looks on the surface in the photo but it is between the elements, I assure you.

Thanks for your replies.
M

[Brian C. Miller]

I recommend that you send it in for servicing before it gets worse. There's no point in waiting for it to grow some more.

[Steven Tribe]

I am not acquainted with this Sinaron - but assume it is a clone of the Rodenstock Sironar type made for Sinar. So it probably has a cemented doublet in front and the "fault" is in the cement layer. Many "crystalisation" faults in balsam are only visable from certain angles. Failures in modern cements are often with complete lack of contact between adjoining surfaces with dramatic areas of "Newton Rings".
But it doesn't look like any cement/balsam fault I have seen. But it doesn't look like fungus, which I believe is unable to thrive on UV glues.
It really does look like the harmless crystallisation that form around tiny impurities in balsam over decades. Perhaps the same thing happens with some modern glues?
This will have no optical/photgraphic consequence and I think it is probably stable now.

[GPS]

It's on the outer edge between the front elements on a Sinaron SE 180mm.
Only visible with certain angles of light, looks like a cross between dust and scratch,
about 3mm long.

Any help is most welcome.
M

I think you yourself answered your question pretty well. It looks like the element scratched some surface with some white stuff with the result of this scratch and a residue on it. Fungus is usually visible not just at some angles.

[Sdrubansky]

Thanks everyone.

I am not acquainted with this Sinaron - but assume it is a clone of the Rodenstock Sironar type made for Sinar. So it probably has a cemented doublet in front and the "fault" is in the cement layer. Many "crystalisation" faults in balsam are only visable from certain angles. Failures in modern cements are often with complete lack of contact between adjoining surfaces with dramatic areas of "Newton Rings".
But it doesn't look like any cement/balsam fault I have seen. But it doesn't look like fungus, which I believe is unable to thrive on UV glues.
It really does look like the harmless crystallisation that form around tiny impurities in balsam over decades. Perhaps the same thing happens with some modern glues?
This will have no optical/photgraphic consequence and I think it is probably stable now.

Very insightful Steve, thanks. Yes, this lens is the same as a Sironar S and
my most used lens, hence the worry.

Since there seems to be no visible effect on image quality
I've decided to let it sit in the sun (should help, whether it's fungus or glue etc.)
and keep a close eye on it from now on. If I see any kind of change
it's going in for repair/cleaning.

Just to clarify: it is definitely NOT a scratch on the front element

M

[GPS]

...
Just to clarify: it is definitely NOT a scratch on the front element

M

Of course not, we believe you. But even the inner element could have been scratched during reassembly and escaped the control because visible just at an angle.

[Steve M Hostetter]

Just for the record, fungus looks like tiny snowflakes

good luck
steve