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Converting M42 lenses to Nikon mount?!
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PostPosted: Wed Sep 23, 2009 10:29 am    Post subject: Converting M42 lenses to Nikon mount?! Reply with quote
Hi guys,

Some days ago I read something about taking apart a T2-Adapter for Nikon and using the Nikon mount the replace the M42 mount on a lense. Is that truly possible?

If so, what are the drawbacks?

Can I focus to infinity with such a converted lense? Do they interfere with the mirror of my D1x?

Would really appreciate some info!


PostPosted: Wed Sep 23, 2009 11:02 am    Post subject: Reply with quote
You can do it with Russian "A" lenses...

http://forum.mflenses.com/some-questions-could-you-help-me-out-t20542.html

Unfortunately there are only a few.


PostPosted: Wed Sep 23, 2009 11:04 am    Post subject: Reply with quote
I don´t think it would be that easy. The register distance different is 1,04 mm and I suppose the M42 thread is shorter than the bayonet to Nikon F. so if You would machine the lens You have to cut extra different between the two mounts dimensions. I know Meyer Optic Goerlitz has the rear part interchangeable for different mount types and the same is with Pentacons I think, but not sure if all their lenses, I would bid only on tele lenses such as Orestor, Telemegor, Orestegor and so on.


PostPosted: Wed Sep 23, 2009 11:37 am    Post subject: Reply with quote
Sure not easy, and I'd think it must depend on the lens, the diameter of it's back lens and if you find a Nikon mount that houses that nicely.
Otherwise I think it should be possible.
The difference in register distance is little hence it will 'almost' focus to infinity and I'd very curious if that in actual use could be enough, DoF would in most cases make objects at infinity being 'in focus' anyway.


PostPosted: Wed Sep 23, 2009 1:11 pm    Post subject: Reply with quote
kuuan wrote:
The difference in register distance is little hence it will 'almost' focus to infinity....


Look at any lens and see how the focusing scale is expanded near the close focus end and compressed near infinity. So a small movement near infinity, either by turning the focusing ring, or by pushing the lens away from the sensor/fim plane by using too large a register, can have a dramatic effect. So on a Jupiter 11A, 4/135, for example, a 1 mm movement moves the focus from infinity to ~ 15 m. On a Nikkor 2.8/28 Ais a 1mm extension moves the focus from infinity to ~ 1m.


PostPosted: Wed Sep 23, 2009 1:49 pm    Post subject: Reply with quote
Thank you for all your answers and for the link to the missing thread! Wink

So it was a dream! Ok, then I will stick to my P6 lenses and save up money for some nice german leica glas...!


PostPosted: Wed Sep 23, 2009 3:39 pm    Post subject: Reply with quote
sichko wrote:
kuuan wrote:
The difference in register distance is little hence it will 'almost' focus to infinity....


Look at any lens and see how the focusing scale is expanded near the close focus end and compressed near infinity. So a small movement near infinity, either by turning the focusing ring, or by pushing the lens away from the sensor/fim plane by using too large a register, can have a dramatic effect. So on a Jupiter 11A, 4/135, for example, a 1 mm movement moves the focus from infinity to ~ 15 m. On a Nikkor 2.8/28 Ais a 1mm extension moves the focus from infinity to ~ 1m.


wow, obviously I was wrong, thank you very much for the correction John!!!


PostPosted: Wed Sep 23, 2009 6:07 pm    Post subject: Reply with quote
I have converted a Jupiter-37A 3.5/135 from M42 to Nikon just by replacing the mount part. Very easy and works perfectly.

But that's a Russian "A" lens, the regular M42-glass will be problematic.


PostPosted: Wed Sep 23, 2009 6:12 pm    Post subject: Reply with quote
You can screw rear lens element in helios 44-3 or 44m series. It will focus to infinity with normal m42/nikon adapter.


PostPosted: Wed Sep 23, 2009 7:45 pm    Post subject: Reply with quote
karabud wrote:
You can screw rear lens element in helios 44-3 or 44m series. It will focus to infinity with normal m42/nikon adapter.


How did you exactly do that? Only the rear element? Or the full optical block? If only the rear element, that not would be loose?


PostPosted: Wed Sep 23, 2009 8:04 pm    Post subject: Reply with quote
horvlas wrote:

How did you exactly do that? Only the rear element? Or the full optical block? If only the rear element, that not would be loose?


Hmm i find it difficult to describe in English well.
Rear element has two small cavity?. I use screwdriver to screw this for about couple mm, but not completely. It works great with 44-3. 44m-4 thos element shakes a little.


PostPosted: Wed Sep 23, 2009 8:18 pm    Post subject: Reply with quote
kuuan wrote:
sichko wrote:
kuuan wrote:
The difference in register distance is little hence it will 'almost' focus to infinity....


Look at any lens and see how the focusing scale is expanded near the close focus end and compressed near infinity. So a small movement near infinity, either by turning the focusing ring, or by pushing the lens away from the sensor/fim plane by using too large a register, can have a dramatic effect. So on a Jupiter 11A, 4/135, for example, a 1 mm movement moves the focus from infinity to ~ 15 m. On a Nikkor 2.8/28 Ais a 1mm extension moves the focus from infinity to ~ 1m.


wow, obviously I was wrong, thank you very much for the correction John!!!


Yes it's not intuitive. An equation (see Wikipedia for example) for a simple converging lens gives the relation between the lens-object distance (S1), the lens-image distance (S2) and the focal length (f) of the lens...

1/S1 +1/S2 = 1/f

Thus S1=(f*S2)/(S2-f)

So for our 28 mm lens focused at infinity S2=f=28 mm. If we now move the lens 1 mm further away from the image (film/sensor) plane, S2= 29 mm, and

S1=(28*29)(29-28 ) = 812 mm ~ 0.8 m which is close to the "1 m" which we esimated from the focussing scale.
Of course the lens is not a simple lens, but the approximation, that it is, works well.
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