Sonnar 1.5 50cm - Front Lens Exchange?

<p>Problem: I have a Sonnar 1.5 50cm for my Contax IIIa, with truly massive separation problems in the rear element.<br>

Possible solution: I'm following an auction on ebay for a similar lens, that is still at the first bid (€1) because the front element is badly scratched. It seems intuitive to get it, and then swap the front element with my lens`s.<br>

Possible problem #2: Both Sonnars are early models, but they clearly do not belong to the same series. The front ring looks different.<br>

Question: are all front elements in all Sonnars exactly identical, so that I can swap them as planned? Or, am I at risk of getting a lens, that will not accept my front element?<br>

I would be grateful for any comment.</p>

 

<p>To clarify further: the potential "donor" is a brass chrome, 12-blades item marked "Carl Zeiss 50mm", but without red T coating (thus, early post-war); the potential "recipient" is a black nickel, 16-blades affair marked "Carl Zeiss Jena 5cm", thus clearly wartime.</p>

 

<p>50cm or 5cm (50mm)?</p>

<p>Trick one this. I thought that the pre and post war Sonnars were the same except for coatings. I would imagine that swapping out elements would be a very trick job, so good luck with that!<br>

I have used various Zeiss lenses with separation and found that they still work fine, albeit with a bit more flare. The scratched front element would cause more problems.</p>

<p>Some years ago there was an article about early post-war Sonnars in a german camera collectors magazine. It was stated that there are quite a few Sonnar fakes, especially in M39 mount, converted from military optics or assembled from stolen Zeiss parts. Zeiss made a public announcement saying that a fake Sonnar probably will not perform like a real one since all the lens elements are matched. <br>

So MAYBE after swapping the front element your Sonnar will not perform exactly as it used to. On the other hand, a non-matched front element may perform better than a matched but scratched one. </p>

<p>Have you looked into the possibility of polishing and re-coating?</p>

<p>Winfried, Mukul: the objective I currently own (50mm) is the one with the separation problem in the rear element. I don't yet own the 5cm one with scratched front lens - I was considering buying it, but only in order to replace the scratched front lens with the good one from the objective I own. Of course, in theory I could also remove the rear element from the front-scratched objective (assuming I buy it) and install this in my own objective (that is, replacing the element with separation). This, however, sounds noticeably more complicated than swapping the front lenses.<br>

Buying the front-scratched objective with the specific idea of having it polished and re-coated does not sound much attractive to me, unless perphaps it comes dirty cheap. My question is, is my proposed swap a feasible solution (apart from the complexity if the transplant operation), or are there reasons (non-matching part, etc.) that would rule it out?</p>

 

The 50mm F1.5 Carl Zeiss lens is different optically from the Carl Zeiss Jena lens.

 

If you will post some photo's of the lens, especially the Namering I can help you sort it out.

 

The Post-War East German lenses are also reformulated. The Wartime lenses are reformulated from the pre-war lenses.

 

The Jupiter-3 is very close to the Sonnar, I've made working lenses out of parts from pre-war Sonnars and Jupiter-3's.

 

http://www.dpreview.com/galleries/876628771/albums/hybrid-sonnar-jupiter-3-5cm-f1-5

Okay- the lens you own is the 50mm F1.5 Zeiss Sonnar, West German. It is a different formulation than all of the lenses marked "5cm" and is NOT compatible with the Jupiter-3. Worse- I have found two versions of the West German 50mm F1.5 Sonnar, slightly different mechanical construction and in production as the same time. I had two West German Sonnars in the same serial number range that had different fixtures, like two production lines. I guess things were hectic after the war.

 

You can "hack" something together, I made a working RF coupled lens out of the front 2/3rds of a Canon 50/1.5 and rear optic of a Nikkor 5cm F1.4. But- it will not be the same as the original.

 

http://www.leicaplace.com/f34/canikon50mm-f1-5-ltm-mount-lens-113/

<p>Many thanks Brian - this does it. There will be no transplant, because donor and recipient are not compatible.<br>

If the price of the scratched lens remains very low, I would buy it nonetheless, and then make some sort of experiment to find out whether massive separation is better or worse than a scratched front lens. As they say here in Germany, it's like the choice between cholera and pest...</p>

 

<p>Good that you now have a direct answer to your question. I am sorry that I mixed up the problems of the two lenses.</p>