Cement failure in rear element

[Ulrich Drolshagen]

Hi all,

lately I bought an old f5.6/150 Symmar. The glass surfaces are perfect and the shutter runs as it should. But by closer inspection there are two tiny spots of lens separation to be seen in the rear element. In the picture the spot near the "edge of the aperture" shows the larger one.



Through a magnifying glass one can see a clear spot shaped like a Ginkgo-leaf. Under some lightening angles it reflects like a fish scale. The seller and I are discussing the consequences this might have in respect of image quality and possible progress of separation. May be these spots are there since the production of the lens some 50 Years ago and nobody noticed or bothered.
Does anybody can share some light on this issue?

Ulrich

[AJ Edmondson]

It looks as if the cement has failed in the spot that is showing and it isn't (in my experience) likely that it is a flaw that has existed since manufacture of the lens. I have used lenses with this type defect with no noticeable ill effects BUT I suspect that under the right lighting conditions it could be detected. As far as I know most of the older lenses were cemented using a balsam cement (in other words a natural resin) and generally this type cement relies on the presence of some residual level of "moisture" to preclude separation.

[CP Goerz]

The malady will have zero effect on the image making of the lens, I've used lenses with far worse spacing than that and they performed perfectly. Good shootin'!

[Peter K]

As far as I know most of the older lenses were cemented using a balsam cement (in other words a natural resin) and generally this type cement relies on the presence of some residual level of "moisture" to preclude separation.

This is only true for realy old lenses. With lenses like the Symmar modern cements are used.

[Ulrich Drolshagen]

This is only true for realy old lenses. With lenses like the Symmar modern cements are used.

The lens is from 1963. As it seems there are two aspects. First, if the separation (or may be inclusion) wasn't there with production, there is chance, it may go on. Second, there seems no way around making a test to see whether it will show up in the picture. I may have the chance this weekend. Then I will settle the issue with the seller. It's a fine lens otherwise, I'm in no way bothered about it's age. I would be sorry having to hand it back.

Thank you all so far

Ulrich

[Ole Tjugen]

There's a big "snowflake" in the rear cell of my 240mm symmar. The only effect I jave ever noticed from it was that I got the lens very, very cheap. No visible effect, even when using the lens converted and stopped down to f:45.

[Jim Galli]

It really won't affect your images. The only thing to settle is what the bid might have ended at if it had been mentioned beforehand. That could be by as much as half. I'm assuming a tyical eblay auction.

[Emil Schildt]

on the other hand: if it looks like mine (see attachment), the faliure looks great, but the lens is useless....

[Archphoto]

That lens is due for a reglue, terrible !

[Emil Schildt]

That lens is due for a reglue, terrible !

if you're talking about my lens, then NO NO!

it is FAR to beautiful to "destroy"...