Question: What is this?

[jdurr]

I acquired these LR lenses and would like some info on what this ring is on the rear elements. Also, what should I do about them?

Thanks

[mpirie]

Looks like balsam separation between the elements.

Very little you can do about it.

Mike

[Dugan]

Are those Rodenstock Sironars? (plain Sironar, not -N)?
There was a problem with separation with early ones, due to adhesive.
Not much can be done about it...try 'em out, see what you get.

[jdurr]

Figures, thanks

[jdurr]

Oh well, thanks.

[Willie]

Maybe you can sell them to Sally Mann? ;-)

[nolindan]

At f22 they may work just fine. As Dugan suggested, try them out.

[ridax]

I own about half a dozen lenses with separations like that - several Rodagons, a Mamiya RB lens and somewhat else.... I actually do not remember which ones exactly, because they all perform just fine. Unlike the classic Canada balsam separation that often makes the lens hazy thus reducing the image contrast considerably, the modern synthetic cement separations with their dichroic mirror appearance just look like a total disaster but actually have almost no effect on the image quality. Years ago, I undertook precise image contrast measurements as well as the sharpness tests with several pairs of identical lenses - the new ones and those with cement separations like shown above - and was really surprised as I just could not detect any image contrast reduction in the separated ones. (As for the sharpness, it just could not (and did not) get worse as the gap between the separated elements is always too tiny to have any influence on the lens aberrations.)

So my advice is: just use them. And if worried about having the glass that's not the best available, borrow some mint lenses of the same type and compare them to your lenses in practice.

The only additional trouble with element separations like the above that I experience from time to time is that when the lens is taken from a cold environment to a warm one, moisture condensation appears not only on the outer glass surfaces but inside the separation, too. And it's not possible to wipe it off from there.

[jdurr]

Thanks, I needed that! Great info. Merry Christmas