West German Contax 35mm f/3.5 Planar Design Question

[das]

Thanks so much to everyone weighing in on this thread. So cool to see folks using the Biometar and Planar on film and digital. Are you folks seeing any focus shift with the Biometar or the Planar? What is really nice about the Biometar is that it can be used with the Amedeo / Coiro adapters, whereas the Planar apparently cannot (without modification to the lens itself).

I don't know if you folks had run across Gigant Optik's review (South Korea) of the Biometar. Very nice photos.

[Zeiss] Carl Zeiss Jena Biometar 35mm F2.8

렌즈명: Carl Zeiss Jena Biometar 35mm F2.8발매년도: 1950년렌즈구성: 4군 5매 최단거리: 0.9m 필터지름: 43mm본체무게: 110g생산개수: 1,614 202 일반적으로 콘탁스 레인지파인더의 35mm 렌즈들은 Carl Zeiss Biogon 35mm F2.8를 필두로 개조없이 라이카에서 사용이 불가능하다고 알려져 있습니다. 그러나 별다른 개조 없이도 어뎁터를 경유하여 라이카 바디에서도 이종교배가 가능한 동독제 칼 짜이스 35mm 렌즈가 존재하는데요, 그럼에도 불구하고 Carl Zeiss...

gigantoptik.com

One thing that the Gigant review states that I don't quite understand is:

"Unlike the West German Contax IIa, which was slightly modified after the war, the flange back is set to the existing Contax I and II, so it can be used on the Nikon RF body without pin correction."

In case you have not seen it, this is also a very informative article about the development and evolution of the Biometar.

Biometar | zeissikonveb.de

Carl Zeiss Jena Biometar. Biometar 80 mm f/2.8. Zeiss Zenzanon. OPREMA.

zeissikonveb.de

A comparison that I would like to do once I get a Biometar is against the W-Nikkor 35mm f/1.8. Although Nikon went symmetrical ala the Leica f/3.5 Summaron with the 1951 35mm f/2.5, it obviously used and then modified the Biometar (or "Xenotar") design for the f/1.8. I wonder how Nikon's addition of a two-element cemented rear group alters the Biometar's results at the 35mm FL. The Nikkor is absolutely outstanding at distortion control, but it is not so strong in the corners at the widest apertures and has quite pronounced focus shift.

 

[dexdog]

NIkon Z6, ISO 100, autoexposure, W-Nikkor 3.5cm, f1.8 in S-mount. My copy of this lens dates to 1960. Point of focus is nearest headlight of truck, about 25 to 30 meters
f1.8

f2

 

[dexdog]

f2.8

f4

f5.6

 

[dexdog]

Not very good conditions for making lens comparisons, but here it is for what its worth. I am also probably not the best person to design such a test!

 

[das]

Just wanted to circle back and say what a great lens the Biometar is. Yeah, a little vignetting wide open but it performs well, on par with contemporaries like the W-Nikkor 35mm f/2.5.

Giganoptik in the ROK had some words of wisdom on this for me. Apparently, and I have never heard this before, but the Biometar was designed to work with prewar Contax RFs. He said that the Biometar works fine with Nikon RFs but would need adjustment to achieve perfect focus with post-war Contax bodies. My bro checked this on an M240 and Amedeo Nikon adapter and it focuses just fine, meaning that no one had modified it in the past 75 years for post war Contaxes.

It's a very cool lens and affordable for how rare it is.

 

[Cascadilla]

Just wanted to circle back and say what a great lens the Biometar is. Yeah, a little vignetting wide open but it performs well, on par with contemporaries like the W-Nikkor 35mm f/2.5.

Giganoptik in the ROK had some words of wisdom on this for me. Apparently, and I have never heard this before, but the Biometar was designed to work with prewar Contax RFs. He said that the Biometar works fine with Nikon RFs but would need adjustment to achieve perfect focus with post-war Contax bodies. My bro checked this on an M240 and Amedeo Nikon adapter and it focuses just fine, meaning that no one had modified it in the past 75 years for post war Contaxes.

It's a very cool lens and affordable for how rare it is.

It seems very strange to me that this lens would have been designed differently to work with older cameras specifically since one thing that didn't change from the Contax I through the IIa and IIIa is the flange distance distance from the lens mount to the film plane. I own and use lots of Zeiss and Nikon RF lenses on my Contax (I,II,III,IIa and IIIa) bodies and have yet to have an issue with lenses coupling to the rangefinder and focusing accurately. I haven't used a 35 mm Biometar, however, to check on this particular lens.

 

[das]

It seems very strange to me that this lens would have been designed differently to work with older cameras specifically since one thing that didn't change from the Contax I through the IIa and IIIa is the flange distance distance from the lens mount to the film plane. I own and use lots of Zeiss and Nikon RF lenses on my Contax (I,II,III,IIa and IIIa) bodies and have yet to have an issue with lenses coupling to the rangefinder and focusing accurately. I haven't used a 35 mm Biometar, however, to check on this particular lens.

It makes some sense given the events of 1950. If you read the German article about the Biometar above, it seems that the real project for Jena was designing a better lens to replace the Tessars on 6x6 Rolleiflexes. Before the Soviets came in and took everything left @ 1950, Jena believed that it could be a principal supplier for Rolleiflex lenses. The 35m f/2.8 Biometar was apparently just an offshoot of that project for Rollei, essentially using the Xenotar/Biometar design to create a proposed 35mm f/2.8 Biogon replacement -- a lens that would in theory perform as well or even better but also be cheaper to make.

I have no idea if this is correct, but it appears that Gigantoptik's theory is that Nikon did not necessarily create a "new" or "different" Contax-style rangefinder system but merely replicated prewar Contax standards. By 1950, I suspect that the postwar West German Contax IIas had not been produced in any quantity yet, so the Biometar was designed to work with prewar Contax standards. The Soviets then shipped off most of East Germany's rangefinder tech to help produce the Jupiters and Kievs. Jena then turned to M42 SLRs.

At the end of the day, the Biometar appears to focus with near 100% accuracy on a Nikon RF, and would probably be a bit "off" with a postwar Contax, but maybe close enough for film use.

 

[Cascadilla]

It makes some sense given the events of 1950. If you read the German article about the Biometar above, it seems that the real project for Jena was designing a better lens to replace the Tessars on 6x6 Rolleiflexes. Before the Soviets came in and took everything left @ 1950, Jena believed that it could be a principal supplier for Rolleiflex lenses. The 35m f/2.8 Biometar was apparently just an offshoot of that project for Rollei, essentially using the Xenotar/Biometar design to create a proposed 35mm f/2.8 Biogon replacement -- a lens that would in theory perform as well or even better but also be cheaper to make.

I have no idea if this is correct, but it appears that Gigantoptik's theory is that Nikon did not necessarily create a "new" or "different" Contax-style rangefinder system but merely replicated prewar Contax standards. By 1950, I suspect that the postwar West German Contax IIas had not been produced in any quantity yet, so the Biometar was designed to work with prewar Contax standards. The Soviets then shipped off most of East Germany's rangefinder tech to help produce the Jupiters and Kievs. Jena then turned to M42 SLRs.

At the end of the day, the Biometar appears to focus with near 100% accuracy on a Nikon RF, and would probably be a bit "off" with a postwar Contax, but maybe close enough for film use.

The difference between Nikon RF focusing and the focusing of all Contax bodies is well known and that difference is the same whether comparing pre war or post war Contax bodies. With wide angle lenses like the 35 mm Biometar, Biogon or Nikkors and shorter focal lengths, it rarely matters. At 50 mm or longer it does, hence Nikon's 8.5 f/2, 10.5 f/2.5 and 13.5 f/3.5 lenses that are marked with a "C" on the focusing ring when they were made specifically for Contax cameras. I have examples of those three lenses and they do focus accurately at both close and long range on my Contax bodies. I haven't read the article you referred to, but I am aware of the state of flux in German optical production in the late 1940's due to the aftermath of WW II. Things might have been very different if the Russians hadn't carted off whole factories and key personnel to Ukraine, and if normal trade relations had continued as they had before the war. But I still don't think that West German Zeiss would have messed with something as basic as the flange focal distance in the design and manufacturing of the IIa and IIIa. And I have read in Zeiss publications from the early 1950's that with the exception of the pre war 35 mm Biogon that the earlier lenses would be fully functional, as has been my experience.

 

[JakobN]

Harry Zöllner, the new head of photo lenses at Carl Zeiss Jena, had an article in the "Jenaer Jahrbuch" for 1951 describing new developments since 1946. About the 35mm Biometar he writes that they made it as the Biogon couldn't be used on the new Contax IIa. But by this time Zeiss Ikon Stuttgart was no longer interested in buying anything from Jena, and Bertele was busy developing the new Zeiss-Opton Biogon.