Bronica lens issue

[revdocjim]

I found a Bronica PG 100/3.5 lens (GS-1) in the junk bin today and grabbed it. There was some bad clouding but once I got it home I took it apart and was able to clean it up pretty well, getting rid of the worst clouding quite easily. But then I discovered another problem. There is a group of two elements near the rear that are glued together and the glue seems to have degraded, causing some rainbow like concentric lines that cover about 25% of the element. I initially probably thought they were just reflections because I didn't notice them at the store but now I see that they are readily visible shining a flashlight through the lens. When the lens is mounted I can't see them through the viewfinder though. Do you think they will affect IQ?

 

[WilliamBDixon]

Yes the problem may also effect focal length. This cement holds the elements together and is optically transparent, with the gap there may be issues.

 

[John Koehrer]

But then, Most likely will have no effect on the image forming properties. It's separation of the elements, the glue is failing and it happens in many older lenses.
You have three choices, Live with it and be happy, send it out for repair $$$$$ or do it yourself. You have an idea how the element comes out so...........
remove it, put the group in acetone to separate the elements and recement them with "crystal clear" from the local hardware. Big box or small should carry it.
People will say it can't be done without collimating it but you can and will never notice a difference. For alignment of the elements I put them back in the barrel until the glue sets,I use a very light coat of Vaseline to keep them from sticking, just enough to see. and use a glossy spray paint for the edges.

 

[revdocjim]

Here's what it looks like from the rear. The rainbow stripes you see on the upper right are the problem.