Classic Nikon RF Lens Compatibility on Classic Contax RF cameras

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gabrioladude

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it is my understanding that the Nikon S cameras from the early fifties were based on the Contax design.

can anyone tell me which of the Nikkor C lenses (that fit the Nikon S) do or do not fit on the Contax IIa

thanks
Frank E (aka Gabrioladude)
 
Nikon telephoto lenses with a 'C' on the side of the lens barrel will mount and focus correctly with the Contax. These include the more common lenses: 8.5cm F2, 10.5cm F2.5, and 13.5cm F3.5. 5cm Normal lenses will focus in front of what the RF indicates, but can be used at F2.8 or so with good results. Wide-angle lenses should work just fine.
 
He's missing something in his explanation- the Nikon camera is calibrated for the Leica standard of 51.6mm and the Contax is ~52.4mm. The helical pitch can be the same, but the travel distance can be shorter and the RF arm of the Nikon calibrated for 51.6mm, and all will work properly.

Shimming alone cannot get the focus to be perfect at close-up and infinity. I moved the helical out on a Nikon S2 5 years ago and use it with Contax lenses. I shimmed it for the sweet spot to be at 8ft, perfect focus as seen through a 15x loupe at the film gate and then the RF adjusted to agree with the actual focus. The DOF of an F1.5 lens is good enough to cover the residual error. It also works with a 13.5cm F3.5 lens made for the Contax.

I've played some other tricks as well: moved the rear group in on a Zeiss Sonnar to shorten the effective focal length, and then shimmed it for the Nikon. Did the same with a Helios-103. Those two lenses can be used close-up and at infinity on the Nikon.
 
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This is very interesting... 0.31mm is a very small diference.
I think that COSINA could create a Nikon/Contax Universal model, whith a Nikon to Contax selector, which could move the lens mount 0,31mm out and in, to get ready to use both systems...

Ernesto
 
It is not that easy, the focal length standard of the two bodies is different. You can use a Zeiss Lens on the Nikon by moving the helical out, but it does sacrifice a little bit at infinity. I have done this, years ago with one of my Nikon S2's. I set the exact focus for 8ft, and the DOF is good enough to use the lens wide-open and close-up. At infinity, it is best stopped down a little bit. The Sonnar focus shift works in your favor.

That point was missed in the explanation on the zeisscamera site.

If you want a Zeiss lens to work at all distances on a Nikon, you need to move the rear group in a little bit to reduce the effective focal length.
 
Brian Sweeney said:
It is not that easy, the focal length standard of the two bodies is different. You can use a Zeiss Lens on the Nikon by moving the helical out, but it does sacrifice a little bit at infinity. I have done this, years ago with one of my Nikon S2's. I set the exact focus for 8ft, and the DOF is good enough to use the lens wide-open and close-up. At infinity, it is best stopped down a little bit. The Sonnar focus shift works in your favor.

That point was missed in the explanation on the zeisscamera site.

If you want a Zeiss lens to work at all distances on a Nikon, you need to move the rear group in a little bit to reduce the effective focal length.
Click to expand...


The reason for the problem you found is that you tried to compensate the diference by adjusting the helical, but what Mr HS says in the Zeisscamera site, is that you should move the whole mount, and in such a case the rangefinder will work for all distances included infinity.

Ernesto
 
ernesto said:
The reason for the problem you found is that you tried to compensate the diference by adjusting the helical, but what Mr HS says in the Zeisscamera site, is that you should move the whole mount, and in such a case the rangefinder will work for all distances included infinity.

Ernesto
Click to expand...

I did move the entire mount. I changed the shims under the mount, moved it out from the body. Refer to Figure 2, "liner" number 81 as described on page 5 of the Nikon SP service manual. I mounted the camera on an optics bench in my lab, took the mount off of the camera, mounted the Sonnar into the mount, set the distance at 8ft, measured a target at 8ft from the film plane, and then shimmed the mount until the image was in sharp focus as seen from the film plane using a 15x loupe. Then I adjusted the rangefinder to agree with the actual focus. It's good enough for the Sonnar to be used wide-open and close-up. This lens can also be used on the Contax IIIa without modification. Why go through all this trouble? I prefer the viewfinder and handling of the Nikon over the Contax. I have 12 Nikkor 5cm F1.4's and 5cm f2's on my Nikon bodies, and just wanted a change for one of them.

I have a second Sonnar that I changed the spacing of the optics. It can only be used on a standard Nikon camera.

I've shimmed, modified, and hacked several 50"ish"-mm lenses for the Nikon. It is calibrated for 51.6mm. Some error will be introduced when using a 52.4mm lens on it. Shimming the mount on the camera can set a sweet-spot where the RF and actual focus agree, but there will be a deviation from actual focus and the Nikon's RF as you move across the range. The Sonnar shift can work in your favor, and infinity focus is quite good at F4 when the shim is set to use the lens wide-open and close-up.

Mr. H.S. is wrong about this. He should stick to Contax.
 
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ernesto said:
The reason for the problem you found is that you tried to compensate the diference by adjusting the helical, but what Mr HS says in the Zeisscamera site, is that you should move the whole mount, and in such a case the rangefinder will work for all distances included infinity.

Ernesto
Click to expand...
The reason for you not to understand the problem very well is that you don't seem to get that there is no helical in the 50mm lenses for both the Contax RF and Nikon RF systems. The helical is built in the camera.

So it is the combination of the camera working distance (helical flange to film plane distance) and the "50mm" lenses optics design which makes it for the not equal native focal lengths of the two "50mm" for these two "similar", yet very different at the same time, systems.

This also explains why any other lens than the 50mm doesn't work better, despite their own built-in helicals, because there the lens helical is mastered by the camera built-in helical as for the pitch.

If things were as simple as Mr Zeisscamera tries to say they are, do you think that Nippon Kogaku would have invested time and money at manufacturing their special 'C' 85, 105 and 135 lenses line for the Contax RF system ?

Brian has it all right and Mr Zeisscamera has it all wrong.
 
Highway 61 said:
The reason for you not to understand the problem very well is that you don't seem to get that there is no helical in the 50mm lenses for both the Contax RF and Nikon RF systems. The helical is built in the camera.

So it is the combination of the camera working distance (helical flange to film plane distance) and the "50mm" lenses optics design which makes it for the not equal native focal lengths of the two "50mm" for these two "similar", yet very different at the same time, systems.

This also explains why any other lens than the 50mm doesn't work better, despite their own built-in helicals, because there the lens helical is mastered by the camera built-in helical as for the pitch.

If things were as simple as Mr Zeisscamera tries to say they are, do you think that Nippon Kogaku would have invested time and money at manufacturing their special 'C' 85, 105 and 135 lenses line for the Contax RF system ?

Brian has it all right and Mr Zeisscamera has it all wrong.
Click to expand...


Well, obviously I think the oposite.
And will prove it now:

You say Nikon normal lens has not the same focal lenght as a Contax normal lens, and also you said that every diferent focal length needs a dedicated helical with a unique pitch.

Ok, so explain me how can Nikon Mount share the same helical pitch with contax mount?

The only answer is: both helicals were designed for a 50mm focal length lens.

Now I will explain why Nikon lenses cannot work properly in contax mount and viceversa:

Because they located the mount at diferent distance from the film plane.

It seems simple to me...

Ernesto
 
It's easy, you are wrong. The Helical on the Nikon does not travel as far. It is made for a 51.6mm Leica standard focal length using a Mount that has the same physical connections as a Contax. The Contax camera uses a longer focal length, nominal 52.4mm. The travel from close-up to infinity is longer on the Contax, or else all of you photo's are out of focus.

Simple rules of Physics.

You simply do not know what you are talking about. Seems really simple to me.
 
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Brian Sweeney said:
It's easy, you are wrong. The Helical on the Nikon does not travel as far. It is made for a 51.6mm Leica standard focal length using a Mount that has the same physical connections as a Contax. The Contax camera uses a longer focal length. The travel from close-up to infinity is longer on the Contax, or else all of you photo's are out of focus.

Simple rules of Physics.

You simply do not know what you are talking about.
Click to expand...

I am sorry but you are wrong.
If the pitch of two helicals are the same, it doesn´t matter if one of them is longer or shorter, they both will move the same distance, if they are rotated the same angle.

http://www.zeisscamera.com/N-C RF Pictures/FrontContaxWNikon.jpg

In this image you can see a mount made with a Nikon and Contax components, that proves they share the same pitch.

Ernesto
 
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They rotate at slightly different angles. The travel is shorter on the Nikon. Or else it would focus past infinity.

You are wrong, or you are claiming the laws of physica are wrong. I side with the laws of physics. I guess others will side with Mr. H.S. I can't help you with that, but I did get an A in Physics.

Now- I've done this modification on a Nikon S2 over 5 years ago. I know that the Sonnar does not quite reach infinity, for a fact. What have you done?
 
The Nikon mount is made for a 51.6mm lens. The distance that it moves from the film as it is focussed between 3ft and infinity is smaller than the distance that a 52.4mm lens moves when focussed between 3ft and infinity.

Again, Have YOU made this modification and tested it with a Sonnar?

I have.
 
Brian Sweeney said:
The Nikon mount is made for a 51.6mm lens. The distance that it moves from the film as it is focussed between 3ft and infinity is smaller than the distance that a 52.4mm lens moves when focussed between 3ft and infinity.

Again, Have YOU made this modification and tested it with a Sonnar?

I have.
Click to expand...

Look at this image:
http://www.zeisscamera.com/N-C RF Pictures/FRings5.jpg
It shows contax and nikon distances, compared.
In fact the contax shows a higer angle compared to nikon, at 3feet.
So, what you say is that they share the same pitch but not the rotating angle, therefore the lens to film plane distance....
am I right?

Ernesto
 
I don;t get the meaning of that image. It does not show how the lens is mounted into position, or its distance from the film. It is irrelevant.

If the helical has the same pitch, then the rotational angle on the Nikon must be slightly smaller than the Contax. The focal length of the lens is the real issue. The focal length of the Nikkor lens is shorter than the Contax lens. Not by much, but it is a real effect that cannot be covered by the DOF. The travel of a 51.6mm lens is less than that of a 52.4mm lens as it crosses the range from 3ft to infinity. There are ways to deal with this, one is moving the point of exact agreement when using a Sonnar on a Nikon. It shifts the error, and more effectively uses the DOF to cover the residual error. The seocnd way is to reduce the focal length on the SOnnar by moving the rear module in. The third way would be to change the RF calibration of the Nikon, increase its eccentricity.

But simply shimming the focus mount as I have done shifts the error, and cannot be used for perfect focus at both near and far distances.
 
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