Rodenstock Omegaron 135mm - What Am I Looking At

Because someone will rightfully ask, no, I haven't tried printing with it yet. So no, I don't know how, or if, it affects printing. I'm moving some things around in my darkroom, and won't be able to print for a bit. When I do, I'll report back.

In the meantime, what am I looking at? Separation? A water spot? Fingerprint? One or the horsemen of the apocalypse?

The lens came with an enlarger I recently acquired that had been in storage for who knows how long and under what conditions. Th enlarger itself was in good shape, so I'm thinking whatever it is, wasn't a result of storage conditions, but rather something that predates them. Thoughts?

From your photo, I'd say that looks like separation.
Possibly from temperature fluctuations in storage?
Rodenstock had an issue with a synthetic lens cement separating at one point in time...(plain Sironar, not "Sironar-N").
Maybe some Omegarons were affected, too?

My 150mm Rodenstock enlarging lens has the same affliction. It does not seem to have any impact on enlargement - at least not b&w. Storage conditions could definitely help cause or exacerbate this - freezing and thawing, for instance.

I had the same idea as well with it being balsam separation.

About 9 years ago I dropped my APO 50mm/2.8 Rodagon into a bucket of water (don't ask!) It was stripped by an independent repairer and cleaned and the diaphragm lubricated and so far there has been no problem with it! Yours may have been the result of creeping dampness over a period of time, alternated with the heat of the bulb creating the start of separation

Thanks, all. I'll report back when my darkroom is back in order.

After Rodenstock moved from balsam lens cement there were issues with some lens designs and separation with their new synthetic optical cement. Around 18 years ago I posted a thread on another forum about a 150mm Sironar lens with similar separation and the reply from a Rodenstock distributor was this occurred where two elements with quite tight radii were cemented together. It only affected Rodenstock lenses made in a relatively short time frame.

The issues had been resolved by the time Rodenstock released the Sironar N & S lenses. I have two Rodagons with separation, one more severe than the other. I've not used them, they came with my De Vere 5108 enlarger, as I already the same or close FL enlarger lenses.

It's more a heat issue with expansion/contraction of differing glass elements, damp if significant would cause rust on the aperture blades first.

Ian