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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