Vickko
Veteran
So, from reading Stephen Gandy's site, the issue is that the Nikon 5cm RF lens focal length is actually 51.8mm, versus the Contax 5cm f1.5 lens focal length is 50.0 mm, and the Nikon RF rangefinder mechanism is designed for the 51.8mm focal length.
And according to S.Gandy, the issue is NOT the lens mount flange distance; that is identical for both Contax and Nikon lenses.
Okay, I understand all that.
My question has to do with the wider focal lengths, namely using Contax IIa 21mm and 35mm Biogons on Nikon RF bodies. What were their focal lengths? And for the Nikon, what precise focal lengths did Nikon use for 21mm and 35mm? They same as Contax?
Are the 21mm and 35mm Biogons perfectly fine on Nikon RF bodies, and not just because the DOF effect accommodates the issues?
regards
Vick
And according to S.Gandy, the issue is NOT the lens mount flange distance; that is identical for both Contax and Nikon lenses.
Okay, I understand all that.
My question has to do with the wider focal lengths, namely using Contax IIa 21mm and 35mm Biogons on Nikon RF bodies. What were their focal lengths? And for the Nikon, what precise focal lengths did Nikon use for 21mm and 35mm? They same as Contax?
Are the 21mm and 35mm Biogons perfectly fine on Nikon RF bodies, and not just because the DOF effect accommodates the issues?
regards
Vick
wes loder
Photographer/Historian
Contax and Nikon RF mounts
Contax and Nikon RF mounts
I believe that Steve Gandy is incorrect concerning the reasons for the differences between the Contax and Nikon RF mounts. First of all, the external mounts have exactly the same flange to focal plane distance. So if you are using an external mount item and not using the rangefinder, you should have no problem. If you set a external-mount lens at infinity, you should have no problem. Secondly, the difference in focal length between the normal Nikkors and the normal Zeiss lenses is not significant enough to cause a problem. In fact, the focal lengths often overlapped due to normally-occurring variations in the manufacturing process. The RF Nikkors are supposed to be 51.6mm, and Zeiss normals slightly longer, but the actual focal lengths do vary and do overlap.
The problem comes from the Nikon's use of a Leica-based rangefinder system. This links the focusing wheel and the prism in the rangefinder to a cam that rides against the back of the helical. The Contax uses a direct gear link between the prism and wheel and the helical. As a result, the pitch of the Nikon's built-in helical is different from the pitch of the Contax. As a result, the optics change focus at different rates, yielding increasing inaccuracies as the lenses are focused closer. This should not be a problem with wide-angles due to the the depth of field that masks the problem. This is why Nikon never made wide-angle Nikkors in special Contax mount. It can be a problem with normals. Many people on this site have compensated for this problem by resetting the mounts so that perfect focus is in the middle of the range instead of at infinity. This also masks the problem. Long-focus, telephotos will be correct at infinity, but due to the difference in the helicals, will move increasingly out-of-focus as the lens is focused closer. Stopping down helps, but will not fix that problem.
Go ahead and use any wide-angle on either camera. They should work. However, note that while the external flange distance does not vary, the gap between that flange and the face of the cameras do vary. Early Nikons and Contaxes have more clearance than the later Nikons (SP, S3). As a result, a Zeiss lenses may not "Turn" onto a late Nikon. Early normals may not fit later Nikons for similar reasons of fit.
There has been much discussion of this here, and in the Nikon Journal, but No one seemed to have actually gone to the trouble to measure true focal lengths of a range of Zeiss and Nikkor lenses, so I believe what I have just stated to be true until such tests are made. Cheers, WES
Contax and Nikon RF mounts
I believe that Steve Gandy is incorrect concerning the reasons for the differences between the Contax and Nikon RF mounts. First of all, the external mounts have exactly the same flange to focal plane distance. So if you are using an external mount item and not using the rangefinder, you should have no problem. If you set a external-mount lens at infinity, you should have no problem. Secondly, the difference in focal length between the normal Nikkors and the normal Zeiss lenses is not significant enough to cause a problem. In fact, the focal lengths often overlapped due to normally-occurring variations in the manufacturing process. The RF Nikkors are supposed to be 51.6mm, and Zeiss normals slightly longer, but the actual focal lengths do vary and do overlap.
The problem comes from the Nikon's use of a Leica-based rangefinder system. This links the focusing wheel and the prism in the rangefinder to a cam that rides against the back of the helical. The Contax uses a direct gear link between the prism and wheel and the helical. As a result, the pitch of the Nikon's built-in helical is different from the pitch of the Contax. As a result, the optics change focus at different rates, yielding increasing inaccuracies as the lenses are focused closer. This should not be a problem with wide-angles due to the the depth of field that masks the problem. This is why Nikon never made wide-angle Nikkors in special Contax mount. It can be a problem with normals. Many people on this site have compensated for this problem by resetting the mounts so that perfect focus is in the middle of the range instead of at infinity. This also masks the problem. Long-focus, telephotos will be correct at infinity, but due to the difference in the helicals, will move increasingly out-of-focus as the lens is focused closer. Stopping down helps, but will not fix that problem.
Go ahead and use any wide-angle on either camera. They should work. However, note that while the external flange distance does not vary, the gap between that flange and the face of the cameras do vary. Early Nikons and Contaxes have more clearance than the later Nikons (SP, S3). As a result, a Zeiss lenses may not "Turn" onto a late Nikon. Early normals may not fit later Nikons for similar reasons of fit.
There has been much discussion of this here, and in the Nikon Journal, but No one seemed to have actually gone to the trouble to measure true focal lengths of a range of Zeiss and Nikkor lenses, so I believe what I have just stated to be true until such tests are made. Cheers, WES
Wes,
You don't seem to understand what I wrote, much less the differences between the two mounts. http://cameraquest.com/NRF-Contax.htm
Of course the external mount flanges are the same between Contax and Nikon RF. That is not the problem for incompatibility.
The problem is the helical built into the camera body. They are engineered to focus different focal length lenses. At infinity it will make no difference, infinity is infinity. For 50 and longer lenses focus issues will show up between the two mounts wide open and close up. As lenses are stopped down and the focus distance is increased DOF begins to cover those differences. For the wide angles the helical errors make little difference real world. 35 and wider Contax and Nikon RF lenses are considered interchangeable, even though there are very slight focusing issues which most shooters will never notice in practice.
Stephen
You don't seem to understand what I wrote, much less the differences between the two mounts. http://cameraquest.com/NRF-Contax.htm
Of course the external mount flanges are the same between Contax and Nikon RF. That is not the problem for incompatibility.
The problem is the helical built into the camera body. They are engineered to focus different focal length lenses. At infinity it will make no difference, infinity is infinity. For 50 and longer lenses focus issues will show up between the two mounts wide open and close up. As lenses are stopped down and the focus distance is increased DOF begins to cover those differences. For the wide angles the helical errors make little difference real world. 35 and wider Contax and Nikon RF lenses are considered interchangeable, even though there are very slight focusing issues which most shooters will never notice in practice.
Stephen
Highway 61
Revisited
Probably given that DOF is deeper behind the focus plane than in front of the focus plane (which has been proved at least), I've personnaly experienced that the best choice to match the two systems is to use Zeiss wides on a Nikon RF body, not Nikon wides on a Contax RF body. I.e., I've got some (tiny, but there yet...) focus errors at close-up using a W-Nikkor-C 2.5/35 on a Contax IIa, while I got tack-sharp close-up shots using a Biogon 2,8/35 on a Nikon S2.
This would mean that you get back-focus using a Nikon lens on a Contax and front-focus using a Zeiss lens on a Nikon RF camera, but I'm now so totally confused with this question after having read all those stories of the Nikon S leather which would cause skin cancer because of its chromic acid that I'd let the gurus confirm or deny what I found using my gear in the field... :angel:
This would mean that you get back-focus using a Nikon lens on a Contax and front-focus using a Zeiss lens on a Nikon RF camera, but I'm now so totally confused with this question after having read all those stories of the Nikon S leather which would cause skin cancer because of its chromic acid that I'd let the gurus confirm or deny what I found using my gear in the field... :angel:
Hmmm this is a dangerous topic ..... bordering on a political discussion, or maybe even a discussion about football 
Vick, do you have both camera systems?
If so take a look at how much the focus helicoid rotates to go from infinity to 0.90m. IMO this is the critical point!
To go from infinity to 0.90m (minimum focus), the focus helicoid on a Contax camera has to rotate around 10 degrees more than the focus helicoid on a Nikon camera.
Vick, do you have both camera systems?
If so take a look at how much the focus helicoid rotates to go from infinity to 0.90m. IMO this is the critical point!
To go from infinity to 0.90m (minimum focus), the focus helicoid on a Contax camera has to rotate around 10 degrees more than the focus helicoid on a Nikon camera.
Tom A
RFF Sponsor
Theories are fine - I apply practicality to it. I use the 21f4.5 Biogon, 28f8 Tessar, 35f3.5 Planar and 35f2.8 Biogon (Prewar) as well as a couple of Sonnar 50f1.5's on my Nikons. Using the Sonnar's @ 1.5 and close (1-3 meters) you get a shift. Stopping them down to f2.8 - no visible shift.
The 35's work fine, particularly the Planar 35 with its f3.5 as its widest aperture. The Biogon 35f2.8 gets a bit fuzzy edges @f2.8 and 1 meter. Not a big problem though. However, it has a tendency to flare.
The Tessar 28f8 has enough depth of field to park a truck in it. Great little lens and as it does not couple to the rangefinder I tend to shoot it @ f11 - f16 anyway.
The 21f4.5 works perfectly throughout all apertures and distances.
I had the Sonnar 85f2 and that one showed a lot of focus shift, even at f4 it was significant and a mid distances too.
I would say that all the Zeiss wides are fine, The 50's is a bit trial and error. There are of course "sample variations" among these lenses too.
My favorites here are the 21f4.5 Biogon and the 35f3.5 Planar. The Tessar 28 is fun, though it is a very "straight rendering" lens - but a maximum aperture of f8 is a bit of a bother.
The 35's work fine, particularly the Planar 35 with its f3.5 as its widest aperture. The Biogon 35f2.8 gets a bit fuzzy edges @f2.8 and 1 meter. Not a big problem though. However, it has a tendency to flare.
The Tessar 28f8 has enough depth of field to park a truck in it. Great little lens and as it does not couple to the rangefinder I tend to shoot it @ f11 - f16 anyway.
The 21f4.5 works perfectly throughout all apertures and distances.
I had the Sonnar 85f2 and that one showed a lot of focus shift, even at f4 it was significant and a mid distances too.
I would say that all the Zeiss wides are fine, The 50's is a bit trial and error. There are of course "sample variations" among these lenses too.
My favorites here are the 21f4.5 Biogon and the 35f3.5 Planar. The Tessar 28 is fun, though it is a very "straight rendering" lens - but a maximum aperture of f8 is a bit of a bother.
Vickko
Veteran
Thanks all.
I like what I'm hearing - i.e use the Contax wides on the Nikon body.
That leaves me with the Sonnar 5cm f1.5 and 85mm f2 to deal with. I suppose I'll have to keep the IIa body for those two lenses.
After a night of shooting with the Contax IIa and the Nikon SP, I was thinking, maybe selling the IIa.
....Vick
I like what I'm hearing - i.e use the Contax wides on the Nikon body.
That leaves me with the Sonnar 5cm f1.5 and 85mm f2 to deal with. I suppose I'll have to keep the IIa body for those two lenses.
After a night of shooting with the Contax IIa and the Nikon SP, I was thinking, maybe selling the IIa.
....Vick
Tom A
RFF Sponsor
Vick, check with brian Sweeney - he can probably shim the f1.5 and the f2 to match the Nikon.
Gary Sandhu
Well-known
Recent experience using Amedeo contax adapter on leica m8: 50/1.4 nikkor 2000 reissue does not focus at 1.4 and within ~6 feet. Smaller aperture is fine.
enasniearth
Well-known
Biogons
Biogons
I have used the postwar zeiss biogons on an s2 nikon with no focus problems , both the 21mm4.5 and the 35mm2.8 . The 35 opton version is fantastic with color slide work .
The wartime biogon t coated and earlier non coated 35 biogons work well
However watch when mounting them as they have larger mounting rings and may scratch or score the chrome nikon front plate .
Used a collapsible 5cm f2 sonnar on an early s2 it went on very tight ,
Did not have it long enough to critically test focus at close distances ,
Used mostly outside on a trip . So can not verify that lens .
Used the option 35 2.8 biogon extensively for several years in many light
Conditions always sharp with beautiful color rendition . Had a Nippon kogaku 35 bright line black finder with it on the s2
As far as what Stephen at camera quest stated the contax standard focal length is slightly longer than the nikkors which are based on the leica standard .
The main problem is the pitch of the helicoid which the japenese assumed was metric on the German cameras , in reality it is English threads per inch .
So the distance to the film plane is the same on the outer bayonet of the con tax and nikon . As you focus closer the pitch of the thread in the mount results in a different location onthe focus scale for the 3feet mark on the two cameras . If you view them side by side this obvious
The contax wide angles are keyed to the zeiss pitch . The nikkors are keyed to the nikon pitch . There is in reality a slight error , this is more than taken up by depth of field which is quite a bit larger than the error even wide open with the biogons . The nikkor wide angles work on the contax as well , the one exception is the 3.5cm 1.8 nikkor at close distances . If I remember on a contax. Iia the 1.8 is off slightly wide open at 3 feet .
Biogons
I have used the postwar zeiss biogons on an s2 nikon with no focus problems , both the 21mm4.5 and the 35mm2.8 . The 35 opton version is fantastic with color slide work .
The wartime biogon t coated and earlier non coated 35 biogons work well
However watch when mounting them as they have larger mounting rings and may scratch or score the chrome nikon front plate .
Used a collapsible 5cm f2 sonnar on an early s2 it went on very tight ,
Did not have it long enough to critically test focus at close distances ,
Used mostly outside on a trip . So can not verify that lens .
Used the option 35 2.8 biogon extensively for several years in many light
Conditions always sharp with beautiful color rendition . Had a Nippon kogaku 35 bright line black finder with it on the s2
As far as what Stephen at camera quest stated the contax standard focal length is slightly longer than the nikkors which are based on the leica standard .
The main problem is the pitch of the helicoid which the japenese assumed was metric on the German cameras , in reality it is English threads per inch .
So the distance to the film plane is the same on the outer bayonet of the con tax and nikon . As you focus closer the pitch of the thread in the mount results in a different location onthe focus scale for the 3feet mark on the two cameras . If you view them side by side this obvious
The contax wide angles are keyed to the zeiss pitch . The nikkors are keyed to the nikon pitch . There is in reality a slight error , this is more than taken up by depth of field which is quite a bit larger than the error even wide open with the biogons . The nikkor wide angles work on the contax as well , the one exception is the 3.5cm 1.8 nikkor at close distances . If I remember on a contax. Iia the 1.8 is off slightly wide open at 3 feet .
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