Schnieder balsam seperation question.

[philldresser]

Just received a pair of lens cells (Schneider 150 Symmar - S) and the rear cell cluster has some balsam seperation of roughly 2 mm into the glass for approx 270 degrees of the lens. I can see that this visibily distorts the image when looking with the eye but would it be a problem when the lens is stopped down? I only use f22 and smaller.

Phill

 

[photobum]

Phill; I have a very old Wollensak triple convertible with some edge seperation on the rear cell. Stopped down to f/16 it is razor sharp through out the field. No big deal as this is a 8x10 lens.

The "yeah but" part is, that I would wonder about a lens as new as a Schneider S having seperation.

 

[eumenius]

Phill,
I don't want to disappoint you, but if such a new lens suffers from separation in rear element, it probably should find its way to bin. But if the defect is small, the best way to test the lens is to shoot with it on different apertures and with strong backlighting. The test will tell you if you're losing sharpness and contrast. On f/22 or smaller the defect should be not too visible, unless it diffuses too much light - that's the rear element, alas. What surprises me, it's how comes it started to separate?? Apparently no one uses Canada balsam now, it's replaced for long with UV-curing cements, so a gentle heating of the lens probably won't help at all.

 

[philldresser]

I checked on the Schneider site and this lens was constructed in 1982 according to the seriel number. They are also linhof selected. Was balsam still used then?

The symptoms are a oil on water film look upto about 2 mm into the lens which I think is lens seperation.

I mounted the lens onto a copal 0 shutter this afternoon and also onto a lens board, so I will hopefully give it a try next weekend or one night during the week.

Phill

 

[Dave Miller]

The symptoms are a oil on water film look upto about 2 mm into the lens which I think is lens seperation.
Phill

I think you are right Phill, I've several like this, in fact one is much worse than you describe, but it still works well at f22.

 

[Gerald Koch]

Soaking in acetone, toluene, or xylene will dissolve the canada balsam and will not damage any coatings. The coatings are usually metal oxides which are not soluble in organic solvents.

 

[wilhelm]

There was a good post about how to separate and recement cemented elements on Usenet the other month. I can't find that particular article I had in mind, but here is a whole thread from the same guy talking about the same process. I found a few other helpful articles by searching Google Groups for stuff like cementing elements and balsam separation.

Hope that helps.

 

[BrianShaw]

Just out of curiousity... will Schneider (Century) repair service fix this kind of problem?

 

[Steve Hamley]

Allegedly the "oil on water" separation has minimal affect on the image. The crystalized balsam and dark edge separation I believe does have an effect stopped down or not, but will of course be on the outer edge of the image circle. In my experience if you have say, a filter ring vignetting, you can't get rid of it by stopping down - I figure edge separation is the same, provided the lens was designed to use that part of the glass.

John van Stelton at Focal Point will recement at $180 per cemented joint, something you probably don't want to undertake to end up with a $200 lens. There are other people who will do it for less.

Steve

 

[MichaelBriggs]

I checked on the Schneider site and this lens was constructed in 1982 according to the seriel number. They are also linhof selected. Was balsam still used then?

The symptoms are a oil on water film look upto about 2 mm into the lens which I think is lens seperation.

......

Phill

I don't know for sure, but I rather doubt that a 1980s lens would use Canada Balsam. Better lenses were made with synthetic adhesives starting in WWII. The synthetics offer many advantages to the lens manufacturers; it doesn't seem likely that Schneider would still be using balsam in the 1980s.

It may not be cost effective to repair a 150 mm Symmar-S.

Schneider will give you an estimate: Dead Link Removed

If you want to repair it yourself, the most difficult part would probably be getting the elements sufficiently aligned.

The best approach may be to ignore the separation, since it is in the rear. Probably at taking apertures the aperture will block light from reaching the separation. Try seeing if the combination of the lens barrel and aperture (at taking aperture) permits light to reach the separation).