Post war Carl Zeiss SN 1608xxx - strange discoloration

[sparrow6224]

I'm not even sure if discoloration is the right word. Looking into the front of the lens w/o a light shining through, with diaphragm closed or partially closed, very plain to see all around the edge of the bottom of the front element or top of the next one, a scalloped pattern of reflective discoloration. Shine a light through the lens from either direction, you cannot see it. No light, there it is. Looking at it from the back -- again, no light, straight on I cannot see it; when I tilt the lens I see it as a dim shadow slightly darker than the glass around it. The pattern is as I say scalloped. Imagine that something leaked a little way into the lens all around the circumference of the element and stained it but only got 3-4 mm. It's like a second diaphragm closed down to f/2 or so.

Any ideas what this is? Again, keep in mind, with a light shining through, you cannot see it. Which I think eleminates haze, no? As would the pattern? And it's not fungus -- it really looks like a coating that only got washed on around the edges.

Oh, and, there's no "T" on the lens.

thanks for any ideas.

[dexdog]

Not sure about the discoloration, but dos not sound like lens separtion or haze, both of which would show up strongly in light shown through the lens.

With regard to the other question,the Carl Zeiss lenses were not marked with a "T". The last post-WW2 lenses from West Germany to be marked with a "T" were the Zeiss-Opton lenses. Carl Zeiss lenses are coated, but not given a "T" marking because by 1954 or so, it was standard practice to coat all lenses, and the T was dropped.

[Jack Conrad]

Going by your description, I'd say it's separation.

[sparrow6224]

I have just taken a test roll that includes this lens, but not had a minute to develop it yet. How does separation affect the image? Ie what should I look for? Unhappy children? Sudden drop in grades? Father starts dating floozies?

Sorry, just kidding. Really, though what should one look for in the images?

[Dez]

Until the separation starts covering a significant portion of the area of the affected elements, you probably won't notice any effect. As it gets worse, you will start seeing a gradual and slight drop in resolution and contrast. i wouldn't worry.

Cheers,
Dez

[S.H.]

Sadly, separation is not uncommon for Zeiss lenses of the period (Contax, Contarex lenses,...).

It can have no discernible effect : I have a Leica lens with a small separation dot (one or two mm2), it does not show on pictures.

[Highway 61]

This is separation due to the use of a synthetic epoxy-like cement instead of genuine Canada balsam at the factory. Like S.H. said, many lenses produced in the very late 1950's and early 1960's at the Oberkochen Carl Zeiss factory do suffer from this problem.

The case is very well documented on the Internet (including very hot threads on the photo forums). The problem can be cured (decementing of the separated elements, cleaning, recementing with modern and steady UV-curing optical cement with a perfect micrometric centering and alignment of the elements to cement) but the treatment will cost twice as much as what an unaffected Sonnar would cost.

As for the photographic results, separation enhances flare and reduces contrast. But the effect depends on how advanced the separation process is.

[sparrow6224]

Thank you all. I'll read more about it.

[farlymac]

I don't have seperation on my Opton lens, but there is a lot of stuff going on in there. However, I've not seen anything in the photos that would indicate a problem. It takes a lot to cause total image degradation. Try to keep your lens out of extremes in temperature, and it should last a long time.

PF