Classic Nikon RF Lens Compatibility on Classic Contax RF cameras

[Sonnar Brian]

That is true. I moved the entire focus mount out so that it would be exact for 8ft. That way, the Sonnar could be used effectively wide-open and close-up. The Sonnar focus shift that occurs with stopping down then helps improve focus at infinity.

I also just looked at my Contax IIIa and Nikon S and S2.

The Contax Helical rotates 270 degrees when moving from 3ft to infinity.

The Nikon S moves less, about 260 degrees. So both mounts can use the same pitch, and the Nikon lens is moved less distance from the film plane while focussing.

 

[ernesto]

Got it!
Thank you very much Brian!
It was a great discussion, and fortunately you were patiente enough!

Yours

Ernesto

 

[Sonnar Brian]

I should have just taken a picture of the IIIa next to the Nikon S when I first read Mr. H.S.'s piece. I 've always known in the "back of my head" that the Nikon rotated less than the Contax. I have not measured it, or put them side by side before. i should have.

I've been hacking these cameras for so long I forget that others do not.

 

[ernesto]

Following the reasoning... Mr HS conclusion would be right for all other lenses except normal lens, since they have their own helical.

E

 

[Sonnar Brian]

Nooo... You have to factor in the translation that other lenses do to the rotation on the internal mount of the Nikon/Contax for the RF to correctly couple to the lens. That is why Nikon made two versions of 8.5cm, 10.5cm, and 13.5cm lenses. The 'C'ontax lenses have to translate to a 270 degree motion, and the Nikon lenses have to translate to that 260 degree motion. It's an issue. I have copies of the 8.5cm F2 and 13.5cm F3.5 in each of Nikon and Contax mount. They are different. They will not focus properly via the rangefinder on the "wrong" camera. I think they will work via scale-focus.

 

[ernesto]

Wow!
This is very tricky!
So, the assumption (I have read at the Cameraquest site) that the wideangle lens works ok in Nikon and Contax bodies is just based in the great depth of field that these lens provides, but in theory there is still a focus shift that is not that easily viewable.

Ernesto

 

[Sonnar Brian]

That is correct about the wide-angle lenses. The focus error is usually covered by the increased DOF. I shimmed a J-12 to be a bit more accurate on the Nikon, again using the 15x loupe and setting the "sweet-spot" for 8ft. You could see the improved agreement using the loupe.

Why did Nikon do this? I like to speculate as much as the next guy. They had already designed their lenses for the Leica standard, they made lenses for the Leica and sold them with the Nicca, and they wanted their camera bodies to "stand out" from the rest of the Japanese manufacturers that went the Leica way. And if the camera flopped, easy to re-engineer as a Leica Thread Mount camera. Look in the back of a Nikon RF and you find a RF Pickup Wheel riding the back of the built in helical. Would not be too hard to substitute a 39mm thread mount for the S-Mount and keep the RF mechanism the same.

 

[wlewisiii]

That new S-mount Sonnar is enough to make me wish it really was simple to go from Nikon to Contax mount. It would look sweet on my '37 Contax III 😉

Good information, as always, Brian.

William

 

[ernesto]

As a conclusion... I wonder how Zeiss Ikon designers decided to put the helical in the mount, instead of providing each lens with its own helical as leica....
Now in 2008 looks nonsense!
Perhaps someone has a good reason, or knows the real story behind this weird desition...

Despite this apparent craziness the Contax mount is very nice, and looks great!

Ernesto

 

[Sonnar Brian]

I always figured they were hedging their bets!

But my Nikons are going to stay bayonet mount...

 

[ernesto]

I am still wondering why they designed the Contax mount that way...
Perhaps someone at[FONT=Helvetica, Arial, sans-serif]The Zeiss Historica Society [/FONT]can answer this question... and provide interesting prototypes photographs too.

Ernesto

 

[Sonnar Brian]

Okay- my take on the lens as an Engineer: The Contax and Nikon mounts allow for better control of the RF coupling than does the Leica. Picking up distance as a function of rotation, either 270 degrees or 260 degrees, is more reliable than trying to follow the RF cam of the Leica style lens. I've had a number of Leica Mount lenses require some fine tuning from slight alignment issues. With the Contax and Nikon mount lenses, you rarely see lenses lose their RF calibration.

In other words- Leica lenses move the RF cam a few millimeters across the range from 3ft to infinity. The mechanical tolerances are tighter, and more prone to problems. I've got a few Leica mount lenses with thin layers of copper tape to correct for 50 years of wear.

 

[Doug]

I suspect most owners of the Contax and earliest Nikon RFs had only the 50mm lens. Wide angle lenses back then were slow and expensive, and the camera's viewfinder shows only the 50mm field of view.

Still, the decision to put the 50mm focus helix in the body had fiddly consequences such as forcing all lenses to focus with the same rotational travel, and also that the entire 50mm lens rotates inconveniently as it's focused.

 

[ernesto]

The Contax and Nikon mounts allow for better control of the RF coupling than does the Leica. Picking up distance as a function of rotation, either 270 degrees or 260 degrees, is more reliable than trying to follow the RF cam of the Leica style lens. I've had a number of Leica Mount lenses require some fine tuning from slight alignment issues. With the Contax and Nikon mount lenses, you rarely see lenses lose their RF calibration.

Brian, again your opinion seems very logical.

Doug, regarding the rotation of the 50mm lens, you are right. That is the reason Zeiss 50mm lens had double f stops scale.
Anyway I have an original shade for a 50mm f2 that has a rectangular shape, and it is impossible to use it for steet scenes becaus you have no time to focus and then correct the shade angle, to press the shutter. That is another problem produced by the rotaing lens...

Anyway they solved it when the primitive colour photography appeared (Dufaycolor System) , and they needed a colour filter that would stay horizontal. They attached it to the outer Contax Mount, so while the inner mount would rotate the other would remain static.
I wonder why they didn´t that with my shade?

E

 

[Shafovaloff1]

FYI, I own a Contax I which had capping problems and in doing repair discovered that the springs etc. from a Contax II and Kiev 4 may be transplanted...I needed to replace the spring for the first curtain. The job is tedious but doable and the results very satisfying! The job is not for the impatient novice but if you take your time and think...it can be done. Just rember you cannot complete the job if you damage the axle for the spring/spool unit as the main difference between the Contax I an Contax II is the side the adjusting slot is on and the way it mounts to the shutter crate.

 

[Erik van Straten]

gelatine silver print (s skopar 50mm f2.5) contax 1 v3

Erik.

 

[Shafovaloff1]

I have the 135mm Nikkor built for Contax and it fits the Contax I,II and IIa nicely......I do have a problem with the Jupiter 12 fitting my Contax I(e) for some unknown reason....it fits the Contax I(f) that I also have without any problem, however, the CZJ Biometar 35mm is very snug against the speed selector on the Contax I...so snug I was, was......considering filing down the lens where it contacts the speed selector....but decided against it since the lens can be removed and the speed group selector moved easily.
Anyone with information about this problem I would like to hear.
Thomas Shafoaloff

 

[flavio81]

As a conclusion... I wonder how Zeiss Ikon designers decided to put the helical in the mount, instead of providing each lens with its own helical as leica....
Now in 2008 looks nonsense!
Perhaps someone has a good reason, or knows the real story behind this weird desition...

Easy:

1. It allows for smaller normal lenses

2. Moreover, the lens will protrude less from the camera body. Check out a Jupiter-8 mounted on a Contax, versus a LTM Jupiter-8 mounted on any LTM camera.

3. It enables the focusing wheel, which some people like (i do) -- you can operate the camera with only one hand!!

4. And, as mentioned by Sonnar Brian, the rotational coupling is more reliable an precise, using this coupling as an helicoid is a bonus.

Genius, really.

 

[Coldkennels]

Okay- my take on the lens as an Engineer: The Contax and Nikon mounts allow for better control of the RF coupling than does the Leica. Picking up distance as a function of rotation, either 270 degrees or 260 degrees, is more reliable than trying to follow the RF cam of the Leica style lens. I've had a number of Leica Mount lenses require some fine tuning from slight alignment issues. With the Contax and Nikon mount lenses, you rarely see lenses lose their RF calibration.

I know I'm responding to an old post (seems to be the order of the day today), but from my non-engineer's perspective, I'd argue that the Contax mount is perhaps more prone to wear-and-tear than the LTM mount was... if you have a collection of LTM lenses, any wear or damage is spread amongst the helicals of all of them. With the Contax having the in-body helical, that's taking all of the strain (and damage from dirt ingress and the like).

My biggest concern with using a Leica vs a Contax is how much they get bumped around in a bag. Put a non-collapsible 50mm on a Contax and it's basically acting like a lever, pulling the in-body focusing helical sideways every time something pushes on it. A non-collapsible 50mm on a Leica seems far more sturdy and less prone to damage in this way.

Maybe I'm over-thinking it, but the lens mount on every Contax and Kiev I've owned, used or held seemed to have a lot more play than even the oldest Leicas I've handled, and I can't help but think this is why.

 

[Sonnar Brian]

The Nikkor 5cm F1.1 was changed from an internal mount to an external mount for this reason.

BUT- for the Sonnar 5cm F1.5 and Nikkor 5cm F1.4 - these are light lenses. I see no wobble on my Contax II and Nikon M.