specific term for issue

[jamaeolus]

Hi guys. I have a Canon FD 50mm 1.4 SSC with an issue I have seen in various lenses from time to time. The darkened edges (ie non optical side parts of lens) are whitened by flaking paint or fungus or something. Does this have a specific term? I imagine it would reduce contrast somewhat as it would increase the amount of light bouncing around in the lens. Thoughts?

[DConvert]

[jamaeolus]

I have seen similar things in folder lenses caused by paint peel. This, I think, is something different. Doesn't look like fungus to me. It looks like maybe the agent used to bond the lens element to the bezel is peeling away. Anyway, I am planning to sell the lens and wanted to describe it without completely scaring off buyers.

[Lightshow]

Looks like the paint is separating from the elements, about the only thing you'll notice is a loss of contrast.
This is an easy fix for a repair tech.

[visualopsins]

Aluminum oxide from the body was my first thought too. Others make me think yes paint peeling off body inside lens mounts. Oxidation building lifted paint. Looks really cool! lol Oofs wide open might look interesting...

[Sciolist]

There's 'Schneideritus' as it's popularly called. As per my Componon here -



I used to ink in the edges of Schneider elements suffering from it until I read often, and realised myself, that it seems to have no impact on performance. I've never looked into what is going on, but looking into 'Schneideritus' might give you a start on tracking down the answer for yours Jameaolus. Just an idea.

[visualopsins]

That looks cool too! lol. Can be seen in oof highlights?

Another thought about the first lens. Suspect since we can see through lens paint peeling from lens body, element edges are unpainted, designers counting on dark paint inside mount instead. Somebody who works on these can tell us are the elements edges painted?

Not sure about these, most 50s are easy to open & clean.

[Sciolist]

[Lightshow]

It's outside the optical path, but it will decrease contrast due to the increased reflectivity.

[ZoneV]

Schneideritis, seen from in and outside:
http://www.4photos.de/camera-diy/Schneideritis.html

[visualopsins]

[jamaeolus]

I have some lenses with schneideritis (though I didn't know it was called that). Also some older folder lenses where it is obvious the paint has disconnected from the edge of the lens and flaked off. This kind of reminded me of delamination though, just the way the weird patterns formed on the side of the elements.

[vivaldibow]

When I was looking for a Vivitar 35mm f2.8 T4 lens, I saw quite a number of them having this "issue".

[SkedAddled]

From the image provided, I would also suggest paint or a blackener applied to a lens element edge
is separating from the glass.

Also from the provided image, I am guessing that the glass edge is a rough finish,
such as a sandblasted surface or from a rougher machining process.
Obviously, it is not a polished surface.

Now, my gut reaction is that I'm looking at a bonded/cemented pair of glass elements,
with the element behind providing a reflection. If not that, then a single element
which was bonded to an outer ring or assembly.
Furthering my gut reaction, and this is because I've seen very similar before
in microscope or telescope or sextant or some other opticals I dismantled
decades ago as a child, is that the blackening has remained firmly affixed to
whatever cement has been used, while coming loose from the rough glass edge.

I saw this same condition when dismantling something optical.
I was a child of about 12 years old, and the item was deemed by adults as worthless.
It was an old item, decades old at the time. I'm fairly sure it was a sextant.
I had free reign to do with it what I pleased, so I dismantled it in my curiousity.
I specifically remember seeing this same condition before dismantling, and found
exactly what the condition was, as I described above.

I may or may not be correct about the issue, but I have experienced almost
exactly the same in first-hand experience.