Dealing with stain on glass element :(

[Zang]

Hi guys,

I have been dealing with a stain on a glass element of Nikkor-Q 135mm f3.5 (Please see the pictures). I have tried all the cleaning methods I know without luck. Do you guys know what this is and how to clean it off?

Cheers,
Zang

[Roland Vink]

I wonder if the lens coating has come off, in which case it is not a stain that can be removed.

[Zang]

I wonder if the lens coating has come off, in which case it is not a stain that can be removed.

I thought only lenses from Nikkor-Q.C version have coating?

[pluton]

I thought only lenses from Nikkor-Q.C version have coating?

The ".C" lenses feature *improved*  ("multiple layer") coatings, but most/all post WW2 Nikkors ...and most post-WW2 lenses from all manufacturers...are coated with at least one layer of magnesium fluoride or similar.  I agree that it looks like the original AR coating has flaked off/been eaten off by moisture or fungus.

[MEPER]

Many Nikkor-Q 135/3.5 has this very nice blue coating if the light hits the right angle.

[Zang]

Many Nikkor-Q 135/3.5 has this very nice blue coating if the light hits the right angle.

Right! I see the same with the lens I have here!