Voigtlander Bessa I - Vaskar 105mm

[michael_frangos]

Hi

I have bought a Bessa I in very good condition, but the lens has a problem. The rear element is loose in its ring (the distance between the glass and the ring is abt 1mm) resulting in out of focus images. Does anyone know how it was held in place? A rubber or metal ring perhaps?

Any advice would be appreciated.

Regards

Michael

 

[rodeo_joe1]

IME, no lens uses a 'rubber ring' to hold elements in place. The usual methods, are either a threaded retaining ring, or the element is swaged into place by turning over a metal edge to permanently seal the lens or group into place. Obviously, a swaged edge can't accidentally work itself loose, but a threaded ring might. The ring would then still be partially screwed into the internal thread, or rattling around loose inside the lens assembly.

 

So, a completely detached element would make me suspect previous deliberate dismantling and incomplete re-assembly of the lens.

 

I suppose it's possible that some sort of cheap circlip or spring retaining ring was used, but that, or its parts should still be inside the lens. Such retaining rings are usually only found on poor quality cheap lenses. Like box camera meniscuses.

[rodeo_joe1]

This thread shows a diagram of the Vaskar, with only a single biconvex rear element. So the good news is that it seems like there's no glass missing. Therefore a simple fabricated spring wire clip would suffice to hold the element in place, or - if you must - a rubber O ring. :confused:

[michael_frangos]

Thanks, rodeo_joe! You were right. That retaining ring could be tightened properly in place...with a rubber tool (vacuum pad? from Japan Hobby Tool) Edited August 30, 2022 by michael_frangos

[rodeo_joe1]

Ah, right! I see how the inner threaded tube screws into the outer lens holder now. There are usually two slots or holes in such retaining rings, but this one obviously needs a 'friction wrench' - i.e. a rubber mat or pad - to screw it home. It might even succumb to a thick rubber glove and good finger pressure.

 

So, nothing missing except a bit of turning force. :)

[John Seaman]

In this situation with unslotted lens retaining rings I have sometimes filed two slots opposite each other, as neatly as possible, in the edge of the ring to facilitate screwing and unscrewing.

[michael_frangos]

It's in place now, I have adjusted focus and tomorrow the camera will be put to the acid test of actual photography.

It was easy to screw the tube in, it's embarrassing that I couldn't figure it out from the start. I tried to screw it pressing from above (it wouldn't move), when pinching(?) it from one side and driving it in was what it needed. Finally, I tightened it with that rubber tool.

 

John, I wouldn't trust myself filing slots as you suggested. The thread is so fine I would be afraid to mess it up.

[rodeo_joe1]

John, I wouldn't trust myself filing slots as you suggested. The thread is so fine I would be afraid to mess it up.

True. Even a machined slot will burr a thread, and you can see such on many factory-made retaining rings. It doesn't usually affect their function though. And a couple of drilled holes shouldn't affect the thread at all.... unless you miss!

[John Seaman]

I didn't mean to cut slots into the thread.

[michael_frangos]

Thank you both for your help! The lens seems to be fine again.