Vintage 3rd party lenses for Nikon RF

keytarjunkie said:
Did you get the Atco from Igor's Camera Exchange? I was watching it for months...wish I had grabbed it...

A fair amount of second hand CV lenses, but especially the 85mm, seem to be developing haze after ~15 years. I wonder what the deal is, and how hard it is to fix. Anyway, please share some more information on your Komura and new Atco lenses!
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No, the Atco actually fell off a truck - happens :)


The glass is clear, with perhaps some faint dust, but pretty darn good actually. The iris is very clean and the focus smooth. I'll test it soon on a Contax IIa - Testing a Retina IIIS at the moment is preoccupying me. (yes it came from Igor!)

Here are some photos:

[url=https://flic.kr/p/2kAf67Z]IMG_2392 by davidociwedu, on Flickr[/URL]

[url=https://flic.kr/p/2kAiAp3]IMG_2399 by davidociwedu, on Flickr[/URL]

[url=https://flic.kr/p/2kAiA29]IMG_2398 by davidociwedu, on Flickr[/URL]

[url=https://flic.kr/p/2kAiANE]IMG_2403 by davidociwedu, on Flickr[/URL]
 
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wes loder said:
It is not a focus discrepancy but a focusing difference. The helicoids have different pitches.
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Hi Wes, are you sure about the pitch being different??

I remember Sonnar Brian writing way back in 2008 (link here) that the pitch is the same, and the difference is due to the Nikon helical rotating 260 degrees to focus from infinity to MFD vs 270 degrees for the Contax helical (same MFD for both systems). Infinity is correct when using a lens with one system on a body from the other system, and the focus error gradually increases the closer you focus due to how the helical movement is translated by the rangefinder system (that 10 degrees of rotation difference). That gels with my experience shooting Contax lenses on Nikon bodies (you get slight back focus close up at wide apertures) but I haven't actually pulled cameras and lenses apart to measure them like Brian has.
 
David Murphy said:
No, the Atco actually fell off a truck - happens :)
Click to expand...

Very nice!!! Thanks for these images, it is quite tall! I like the depth of field scale and font. I look forward to seeing some image samples when you get time to use it. :) I see on flickr you also have the Tele-Tanar 13.5cm f/3.5 and the Zeiss Orthometar 3.5cm f/4.5 (does this one fit on Nikon RF? I think not..).

wes loder said:
It is not a focus discrepancy but a focusing difference. The helicoids have different pitches.
Click to expand...

As Jon also mentioned, I thought the problem was the travel distance of the focus ring to mfd. Discrepancy is the wrong word, and I don't think "difference" really works well either. I'd like to dive further into this though!
 
The Orthometar fits on my Nikon SP without difficulty, and I can rotate through full range of focus. Same goes for the post-WW2 CZJ Biometar.
 
jonmanjiro said:
Hi Wes, are you sure about the pitch being different??

Rotate the built-in helicoid on both a Nikon RF and a Contax. The Nikon helicoid rotates 270 degrees to carry the mount from infinity to its three foot setting. The Contax requires 274 degrees turn to reach the same close focus. That is due to the difference in the pitch of the helicoid. The infinity setting on the Contax and Nikons I have measured is the same, both internal and external. So any lens should be focus correctly at infinity. However, since external mount lenses remain dependent on the internal turn of the helicoid to determine RF focus, the longer the focal length, the more the difference in pitch will matter for focusing accuracy. The focus chart that Voigtländer published for the 85mm lens clearly shows that change. Everything is fine at infinity, but the closer the focus, the bigger the difference. DOF will mask that difference, but not eliminate it. I once owned a 135mm Nikkor in the 'C' mounting, which ignorant me used on my Nikon S2. Most of the photos I took were fine, either because I was using infinity, or a small enough F-stop to mask the focusing problem. Some were out-of-focus, and eventually I learned the reason. You should not have a problem using any wide-angle on either a Nikon or a Contax due to DOF, but longer lenses may be a problem.

On another issue, the depth of the flange of some external mount lenses for the Contax may be tighter than the gap between the mounting blades and the front escutcheon of a Nikon. This will cause the lens to bind and/or scratch the front of a Nikon RF when mounting. The solution is to take some fine emory paper and sand off the back of the lens mount flange. Just a tiny bit of of sanding should work. This will not affect focus since that comes from the front of the lens flange, but will give enough clearance to safely mount the lens. Cheers,
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The mounting of Contax lenses on Nikon SP got me intrigued. I was able to put the Orthometar and Biometar on the SP without damage, so I decided to try a couple of pre-WW2 Biogons. The first one I mounted left tiny little "bright line" scratches from about 3 o'clock to 6 o'clock in the SP. I blacked out the scratched area with a Sharpie and tried the other Biogon, mounting the second lens did not scratch the Sharpie. I cleaned off the Sharpie, the scratched area is visible, but I cannot feel it with a fingernail. I can see the scratch using a 10x hand lens, but I am guessing it is only a couple thou deep.
 
Sadly I had to sell my Orthometar about ten years ago (during the "Great Recession"). Despite being uncoated, like most Zeiss lenses it performed better than one would expect - i.e., quite well. I used it on a Contax IIa at the time, so I can't speak to Nikon RF issues.
 
wes loder said:
Rotate the built-in helicoid on both a Nikon RF and a Contax. The Nikon helicoid rotates 270 degrees to carry the mount from infinity to its three foot setting. The Contax requires 274 degrees turn to reach the same close focus. That is due to the difference in the pitch of the helicoid. The infinity setting on the Contax and Nikons I have measured is the same, both internal and external. So any lens should be focus correctly at infinity. However, since external mount lenses remain dependent on the internal turn of the helicoid to determine RF focus, the longer the focal length, the more the difference in pitch will matter for focusing accuracy.
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Hi Wes, thanks for your reply. I'm still not convinced the pitch is where the difference lies, tbh.

Since the Nikon standard 50mm lens, nominally 51.6mm, is a slightly shorter focal length than the Contax standard 50mm lens, nominally 52.4mm, it would need to be slightly closer to the film plane to achieve correct focus at the same MFD as the Contax lens. Assuming the pitch is the same, that 4 degrees less rotation of the Nikon mount is just the right amount to give correct focus at the same MFD as the Contax lens.

I'm inclined to think the Nikon engineers copied the Contax mount precisely including the pitch, but since they used the Leica standard of 51.6mm instead of the Contax standard of 52.4mm for their standard 50mm lens focal length, they designed the helical to stop 4 degrees shorter where the 51.6mm lens correctly focuses at the MFD of 0.9m, then designed their RF system around that.
 
Henry Scherer is the one that measured the Contax and Nikon helical and pitch of the threads.

http://zeisscamera.com/articles_cnrfdr.shtml

From that article: "But they both have the same thread pitch and this means that for each degree of rotation of the barrel the barrel of the Nikon and the Contax mount will extend from the mount the same exact distance."

He screwed a Nikon helical into a Contax mount. He did not note the difference in rotation between the two systems.

Note from the article, "The conclusion of this work is simply that a Zeiss Contax lens to be used on a Nikon camera must have the lens cartridge moved 0.31 mm further out in the focusing mount and a Nikor lens to be used on a Contax must be moved about 0.31 mm further in.", which was written years after I modified my S2. The extra ~0.1mm that I added makes up for the difference in focal length of the Sonnar.

20 years ago now- I shimmed a Nikon S2 for Contax lenses. Bought a camera from a collector, must have been a shelf queen as it was missing shims under 2 of the mount screws. I used some precision "MWS2" washers, moved the helical out ~0.4mm. Calibrated the RF for 8ft, I've been able to use it with a Contax mount 13.5cm lens, but mostly with a Zeiss Opton 50/1.5.

Several years after adjusting the S2 for Zeiss lenses, I knew what to do for the Jupiter-3 to be used on a Leica.



The difference in focal length between the Jupiter and a Leica is the same as that between a Zeiss Sonnar and a Nikkor "normal" lens.
 
On Contax external Mount lenses scratching a Nikon camera- You need to file a little bit off the back of the lens.

My modified S2 does not have this problem as the mount is extended from the body.
 
This is a discussion that we had on this forum 12 years ago, Amedeo was part of it.
Amedeo uses an Indexed Cam for his dedicated Contax internal mount adapter, and a 1:1 cam for his dedicated Nikon internal mount adapter. The focus for each is perfect on my M9.
 
Scherer compared a Contax I to a Nikon SP. A lot of water under the bridge between those two designs. It would be better to compare a Nikon M with a Contax II. I might also note, that the actual focal length of the 50s varied considerably. Wolbarst's research in 1951 indicated that the Nikkors he tested had actual focal lengths of 52.05mm and 51.92mm compared to a Sonnar of 52.07mm. That sounds a lot closer to the Zeiss design than a Leitz design. My point was that it does not matter what the normal focal length of the lenses is or was, but the difference in the rotation of internal helicoids is what throws the longer, external mount lenses off when focused closer than infinity.
 
Scherer states "I purchased a nice old Nikon S Rangefinder camera and removed the focusing mount from it. A Contax IIa camera focusing mount was also obtained. Both were ultrasonically cleaned to make sure there would be no differences in measurements caused by dirt or dust. Here's a picture of them both side by side. The Nikon mount is on the left:" He states that the thread pitch of the two are the same. These two cameras were in production at the same time.
 
I did a little experiment of my own. I used a M-sync Nikon from early 1951 with a contemporary 50mm f1.4 Nikkor, and a Contax IIa–black dial and a 50mm f2 Sonnar from the late 1930s.

Setting both cameras on T, I mounted a ground glass on the focal plane on each one in turn. I then checked the focus of both the Nikkor and the Sonnar on both the Nikon and the Contax, first at infinity (a wooded hill several miles away). The image that both lenses yielded on either camera were sharp when viewed with a 10x loupe. I then set a target at three feet, set the helicoids at three feet and checked focus again. Both lenses yielded a sharp image on both cameras at that setting.
Both cameras advanced the helicoid by the same distance to go from infinity to the three-foot mark (4.5mm). However, as noted, the helicoid turns 270 degrees to cover that distance on the Nikon and 374 degrees to cover that same distance on the Contax. Looks like a difference in pitch to me.
If there is a difference in actual normal lens focal length, it is less than half a millimeter and in most cases, there may not be a difference at all.
However, the mounts may have changed over time and with changes in models. So to make a final test, one would have to compare a range of Nikon to a range of Contaxes.
I do not trust Scherer.
 
The DOF of the F2 Sonnar will cover the focus error.

When I moved the helical of the S2 farther out it was with the post-war 50mm F1.5 Sonnar from my Contax IIIa. The amount required agrees with what Scherer measured years later. The results on film with the same lens on the IIIa and the modified S2 give a sharp focus.

50/1.5 Sonnar, wide-open on the modified S2.


I looked at my Nikon M and Nikon M w Sync- DOF marks for F2, but not F1.5. The Nikon S- DOF mark for F1.4.

I've shot with 50 or so pre-war and wartime 5cm F1.5 Sonnars, there is variation in focal length. Of those 50: I have 1 (kept it) that was perfect focus at F1.5 across full range on my Nikons.
 
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