There are many explanations of Nikon rangefinder mounts vs Contax rangefinder mounts just on RFF -- not to mention the rest of the net.
Some have explanations about how the differences came about, which may or may not be true.
Who would know better than Amedeo, the master lens adapter maker?
.... THE manufacturer of the best Nikon RF or Contax RF lens adapters to Leica M the world has ever seen.
Amedeo concerns himself not with why but how to make the adapters focus accurately.
According to Amedeo
1) the back focus distance from flange to focal plane is 7.11mm on Contax RF is 7.11mm and 7.09mm on Nikon RF.
That is a difference of only 0.02mm.
Film is about 7.5 to 10 times thicker, usually with a thickness between 0.15 and 0.20mm.
CLARIFICATION FROM AMEDEO
That measure is from the internal bayonet of the adapter to the flange of the Leica body
So shooting with film, the adapter infinity back focus difference is so slight it can go unnoticed, but not on digital which is more demanding.
Thus a Amedeo Nikon Lens Adapter or Amedeo Contax Lens Adapter can appear to have the same infinity focus on film.
Both adapters will focus into the film's cellulose substrate.
Switching to a digital body can show the different infinity focus at wider apertures, but that focus difference can still be lost at small apertures.
Amedeo has no experience with reflex housings, which use ground glass focusing only (not the camera body's built in focusing helical).
With a back distance focus of only 0.02mm I'm guessing most users would not be able to notice a such a small difference in ground glass focus between the reflex housings.
2) Leica rangefinders are calibrated for 50mm lenses. Nikon and Contax rangefinders are really calibrated around 52mm, so the helical of the adapter must move a bit faster, not is a linear movement, and the edge that pushes the rangefinder lever mechanism must be machined on ramp for to have a delay. The delays on Nikon and Contax bodies are different.
I have tried to explain this as best I can, as Amedeo explained it to me.
Stephen
Some have explanations about how the differences came about, which may or may not be true.
Who would know better than Amedeo, the master lens adapter maker?
.... THE manufacturer of the best Nikon RF or Contax RF lens adapters to Leica M the world has ever seen.
Amedeo concerns himself not with why but how to make the adapters focus accurately.
According to Amedeo
1) the back focus distance from flange to focal plane is 7.11mm on Contax RF is 7.11mm and 7.09mm on Nikon RF.
That is a difference of only 0.02mm.
Film is about 7.5 to 10 times thicker, usually with a thickness between 0.15 and 0.20mm.
CLARIFICATION FROM AMEDEO
That measure is from the internal bayonet of the adapter to the flange of the Leica body
So shooting with film, the adapter infinity back focus difference is so slight it can go unnoticed, but not on digital which is more demanding.
Thus a Amedeo Nikon Lens Adapter or Amedeo Contax Lens Adapter can appear to have the same infinity focus on film.
Both adapters will focus into the film's cellulose substrate.
Switching to a digital body can show the different infinity focus at wider apertures, but that focus difference can still be lost at small apertures.
Amedeo has no experience with reflex housings, which use ground glass focusing only (not the camera body's built in focusing helical).
With a back distance focus of only 0.02mm I'm guessing most users would not be able to notice a such a small difference in ground glass focus between the reflex housings.
2) Leica rangefinders are calibrated for 50mm lenses. Nikon and Contax rangefinders are really calibrated around 52mm, so the helical of the adapter must move a bit faster, not is a linear movement, and the edge that pushes the rangefinder lever mechanism must be machined on ramp for to have a delay. The delays on Nikon and Contax bodies are different.
I have tried to explain this as best I can, as Amedeo explained it to me.
Stephen
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zeitz
Established
Stephen, what flange are you referring to for the 7.11 vs 7.09mm measurement?
enasniearth
Well-known
7mm is about 3/8”
enasniearth
Well-known
I pulled out an early s2
I took some really rough measurements
I don’t have any precision instruments
Outer collar to film 38.9 mm
Inner three lugs outer surface to film 30.95 mm (50 lens mount)
3 prong outer bayonet outer surface to film 34.13 mm ( other lenses mount )
These measurements are very rough on my part
If there is only .02 mm difference in the lens mounts that less than 1 thousandth of an inch
I think 7mm is the difference between the Nikon / Contax mount & the Leica flange to film distance
I took some really rough measurements
I don’t have any precision instruments
Outer collar to film 38.9 mm
Inner three lugs outer surface to film 30.95 mm (50 lens mount)
3 prong outer bayonet outer surface to film 34.13 mm ( other lenses mount )
These measurements are very rough on my part
If there is only .02 mm difference in the lens mounts that less than 1 thousandth of an inch
I think 7mm is the difference between the Nikon / Contax mount & the Leica flange to film distance
zeitz
Established
The Contax mount to focal plane distance is always quoted to be 34.85mm, although I can't figure out what feature of the Contax mount is used as a reference. Obviously there are two sets of bayonet taps on the Contax camera, one for normal lens and one for all other lenses. The Leica mount to focal plane distance is well known to be 28.80mm. So the difference is 6.05mm. No one seems to know the mounts better than Amedeo.
I've noticed that the optics sit in the mount slightly differently between the Nikon and Contax.
The Leica is calibrated for a nominal 51.6mm, same as the Nikon standard focal length. The Nikon S-Mount and LTM mount have the same optics.
When looking at the back of my Amedeo S-Mount internal mount adapter and the back of the Amedeo Contax internal mount adapter, the latter has an indexed cam to account for the difference in the Nikon 51.6mm nominal focal length and the Contax 52.4mm nominal focal length.
The RF cam for the Nikkor 50/1.4 moves 1:1 with the optics, the RF cam for the Sonnar 50/1.5 is indexed.
The Nikkor focal length is the same as what the Leica is calibrated for. The Contax focal length is longer, and it needs the indexed cam to account for the difference. The difference- about 0.12mm.
We had a discussion which included Amedeo had here on RFF a long time ago about this.
rangefinderforum.com
The Leica is calibrated for a nominal 51.6mm, same as the Nikon standard focal length. The Nikon S-Mount and LTM mount have the same optics.
When looking at the back of my Amedeo S-Mount internal mount adapter and the back of the Amedeo Contax internal mount adapter, the latter has an indexed cam to account for the difference in the Nikon 51.6mm nominal focal length and the Contax 52.4mm nominal focal length.
The RF cam for the Nikkor 50/1.4 moves 1:1 with the optics, the RF cam for the Sonnar 50/1.5 is indexed.
The Nikkor focal length is the same as what the Leica is calibrated for. The Contax focal length is longer, and it needs the indexed cam to account for the difference. The difference- about 0.12mm.
We had a discussion which included Amedeo had here on RFF a long time ago about this.
Indexed Cams on RF Lenses and Adapters
This thread is intended for discussion on the need to introduce an indexed Cam to adapt lenses made for the Zeiss Contax for use on the Leica. It carries over the discussion started on this: http://rangefinderforum.com/forums/showthread.php?threadid=82986&page=2 Thread. To perfectly match the...
rangefinderforum.com
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enasniearth
Well-known
If you use Leica m flange to film distance it’s 1 mm less than Leica screwmount flange to film plane
7mm total difference Nikon rf to Leica m
34.85 is most quoted to the outside bayonet lugs
7mm total difference Nikon rf to Leica m
34.85 is most quoted to the outside bayonet lugs
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I am quoting Amedeo, something was lost in translation...
Asked him for clarification
Asked him for clarification
enasniearth
Well-known
What Amedeo states makes sense
The 7.11vs 7.09 is close
To the difference between the m mount 27.8
And outside bayonet Contax / Nikon
34.85
Both often stated online
Difference of 7.05 mm
CLARIFICATION FROM AMEDEO:
That measure is from the internal bayonet of the adapter to the flange of the Leica body
The 7.11vs 7.09 is close
To the difference between the m mount 27.8
And outside bayonet Contax / Nikon
34.85
Both often stated online
Difference of 7.05 mm
CLARIFICATION FROM AMEDEO:
That measure is from the internal bayonet of the adapter to the flange of the Leica body
Last edited by a moderator:
wlewisiii
Just another hotel clerk
All I know is that my Amedeo adapter purchased through Cameraquest and using my regular Nikon lenses, or quite often my Sonnar Brian adjusted Zeiss 50/2 collapsible Sonnar, works fine on my Leica M 240 and the focus is within the error margin of my eyes, even when shooting them wide open.
Other peoples eyes may well be more fussy
Other peoples eyes may well be more fussy
1) the back focus distance from flange to focal plane is 7.11mm on Contax RF is 7.11mm and 7.09mm on Nikon RF.
That is a difference of only 0.02mm.
Film is about 7.5 to 10 times thicker, usually with a thickness between 0.15 and 0.20mm.
CLARIFICATION FROM AMEDEO
That measure is from the internal bayonet of the adapter to the flange of the Leica body
That is a difference of only 0.02mm.
Film is about 7.5 to 10 times thicker, usually with a thickness between 0.15 and 0.20mm.
CLARIFICATION FROM AMEDEO
That measure is from the internal bayonet of the adapter to the flange of the Leica body
mdarnton
Well-known
I thought that the difference was the difference of the degrees of rotation from 1 meter to infinity varies between Nikon and Contax.