Cleaning a Carl Zeiss Sonnar 50mm f1.5

[Sonnar Brian]

@simonOWO
There are two different versions of the 50mm F1.5 West German Sonnar- getting the aperture ring off is very different. I think yours is the more difficult version.
That version- as you found out, the set screws couple the ring to the movement of the blades. The "easier" version using a screw in pin like a wartime Sonnar.

What are you trying to do by taking the lens down further?

 

[simonOWO]

@Sonnar Brian

The movement of aperture ring is stiff, feels like some dirty thing got into the threads (if there is any threads under aperture ring like the other type) I am trying to do a CLA, and potentially a color mod of the exterior, make the lens all black

 

[Sonnar Brian]

Try unscrewing the aperture ring towards the back of the barrel once the coupling pin is out.

 

[simonOWO]

It is blocked as if reached f1.5

 

[simonOWO]

I found the pin, it is hiding behind the elements.

After that it is similar to the easier ones.

 

[JBiogon]

Hello Brian,
I have been reading this thread with great interest.
I have a Zeiss Opton 50mm f1.5.
I only want to collimate it, so believe I don't need to dismantle it further than just removing the outer ring at the rear so that the lens body can be removed from the mount.

But my problem is that the outer ring seems to be well and truly stuck. Even applying as much force/torque as I can reasonably do using a lens wrench, it won't budge. What is considered to be the best next move in such a case?

 

[simonOWO]

@simonOWO
There are two different versions of the 50mm F1.5 West German Sonnar- getting the aperture ring off is very different. I think yours is the more difficult version.
That version- as you found out, the set screws couple the ring to the movement of the blades. The "easier" version using a screw in pin like a wartime Sonnar.

What are you trying to do by taking the lens down further?
View attachment 4853550View attachment 4853551View attachment 4853552View attachment 4853553

Looking back at this thread, can we say that we have 3 versions? Inside pin, outside pin, set screw?

 

[Sonnar Brian]

I have had that happen a number of times. What I do: a slight amount of Lighter Fluid or 99% alcohol to free it up. Slight amount, applied to that outer ring. Then- spanner that fits nicely into the slot.

 

[peterm1]

This link may also be of assistance.

Mike Elek: Cleaning a Sonnar lens

elekm.net

 

[Sonnar Brian]

It's been a while- but on the stuck retaining ring problem, I remember removing the rear group to get easier access to the retaining ring. Meaning with the inner rings out of the way, able to get easier access to the slots of the retaining ring.

 

[JBiogon]

Many thanks Brian and Peter.
Indeed I do think it's better to remove the rear group first; I followed your advice Brian. 3 reasons: 1) it allows better access to the stuck outer retaining ring (and if really necessary you could devise a special tool to fit across the castellated slots in the retaining ring, thus giving better engagement and more controlled leverage; 2) you don't risk damaging the rear element in case of accident/slippage; 3) it allows a more direct route for the freeing agent (I used lighter fluid) to get down into the thread, without being potentially obstructed by the ring holding the rear group.

Anyway, mine was well a truly stuck and it took me several goes over a couple of days, but eventually it shifted.
The strange thing is that when it was all apart there was nothing indicating why it should have been so stuck, such as corrosion or muck. I can only think that it had been done up very tight and/or there was some micro adhesion somewhere.

All done now, though, and the lens is back together.

 

[aw614]

This helped out with another Sonnar 50mm F1.5 I got with a broken Contax iiia on offerup. Has two tiny ~1mm scratches on the front element that I can feel with my finger, but the rear and rear middle element needed some cleaning. Aperture is a little bit stiff, not bad, but could be better. Might go at it again.

Shot with it last week with my Oleg CLA's Contax II so hopefully i'll get my results back from it to share. Nearly freaked out when that guide pin fell on the floor on me, but luckily found it.

The uncoated prewar one I got, ended up sending it to get a CLA, I went in from the rear, but i could not get it open and it got stuck on me, the rear element would loosen, then tighten up like it was seized tight. I should have tried the lighter fluid trick mentioned here.

 

[aw614]

Brian by any chance do you have the dimensions of the guide pin? My rough estimate is 2.90mm for the larger diameter circle and 1.30mm for the smaller one. But i dont have thickness

I had to go back into my lens and retighten the small set screws on the aperture and I lost the guide pin. Stupid me forgot all about it just now when it fell. I might as well look into getting some 3d printed copies made...

 

[Sonnar Brian]

@aw614 - I'll have to take one apart and measure it.

 

[Sonnar Brian]

@aw614

I thought this best shown in pictures, but will put some words in as well...
(I'm letting the forum software resize the images from the originals)

The slot in the 50mm F2 and 50mm F1.5 barrel is the same width and shape.


Thickness of the portion that the slot slides over.


End-to-End of the guide pin.


width of the part that the slot slides over.


Width of the head that is seen when mounted in the barrel.


Note position of the head. Maybe to help dislodge the barrel if stuck?


50 F2 and 50 F1.5- same slot.


Guide pin in mount.


In Mount with barrel.

 

[aw614]

Great this is really helpful, it looks like my rough measurements without the guidepin were really close to your measurements. I was slightly off on the total height and of the total diameter of the top portion of the pin. My initial rough guess on the width of the head was 1.30 for some reason instead of your 1.72.

I thought the pin being offcentered allowed the tweaking of where the aperture values landed on the hash marks, at least that was my observation when I saw I could rotate it around

 

[Sonnar Brian]

I thought the pin being offcentered allowed the tweaking of where the aperture values landed on the hash marks, at least that was my observation when I saw I could rotate it around

That makes perfect sense!