Ugly last lens element

[Anu]

The lens seems to be in perfect condition, other than the last element which looks like this:



Do you think this lens is hopeless?

[Attila]

Might be yes , might be not. Which lens is this ? I have lens with this looking rare element and works fine.

[Arkku]

Lenses are very resilient to dirt and scratches on their elements, especially the front. Rear elements may be problematic, especially with digital cameras due to reflections from the sensor, but I have a lens with rear element coatings completely eaten by fungus and some scratches on top of that, and it doesn't seem to do anything other than lower contrast.

[dnas]

Is that on the back surface of the lens??

It could be fungus, as it can look like that sometimes.

Get a q-tip with a little distilled white vinegar on it and give it a once over, and clean with a new lens tissue immediately. If there is any vinegar residue you can see, just repeat.
Finish up with distilled water, and clean with a new lens tissue.

[Anu]

I must apoligize first as I made the post just to see what kind of answers I'd get

I had actually tested the lens before, and had tried to clean the element - it seems it is not fungus, but just the coatin has deteriorated for whatever reason.

Anyhow, the lens in question is CZJ 180/2.8 Sonnar (zebra), and it delivers the image quality one would expect: simply excellent resolution and bokeh! I was surprised that back element didn't cause any visible problems (contrast may be slighty less, maybe). Very happy with the lens - the only problem is that I had to attach it to the camera with a m42 adapter from 300/4 and it is lacking the ring that holds the adapter tightly in the p6-mount. Anyone have a spare?

[estudleon]

Not surprise to me. I see a lot of CZJ 2,8/180 with glass problems.

Could be that has glass with some aluminium component (as old leica M lenses)?

[Attila]

Most people are too picky about lens problems even if 90% of lens problems not effect lens quality or effect only minimal. Enjoy this great lens and share some beautiful photos taken with your zebra.

[Anu]

I do like the four leaves on the bottom.

[supahmario]

the colors in #2 are balm to my eyes!

[Photomac]

There is a very interesting paper on the Schott website, about the chemical properties of optical glass. http://www.schott.com/advanced_optics/english/download/tie-30_chemical_properties_of_optical_glass_v3.pdf
The presence of moisture in small quantities causes exactly the kind of deterioration described here (can't tell for sure without examining the element). The bad news is that it can't be cleaned off or have the coating removed (and re-coated or not), since it is breakdown of the surface layer of the glass itself. It's effects can be minimised, but that's all.

Regards

Angus

[orly_andico]

some automotive polishing compound could take that stuff off... (if it's on the outer side of the rear element)

i've successfully used polishing compound to take off damaged coatings -- yes it removes lens coatings quite efficiently. and so long as you don't rub for too long, it will not affect the figure of the lens.