Wonder Why?

[ernesto]

Hello,

I have just ordered my contax sc adapter to VM and the Close Focus adapter from VM to E mount that should work together.
While looking for info in the web I found that Cosina made two versions of the first adapter, one for Nikon and the second for Contax.
https://shop.cameraquest.com/voigtl...unt-to-vm-mount-adapter-for-vm-e-close-focus/
https://shop.cameraquest.com/voigtl...unt-to-vm-mount-adapter-for-vm-e-close-focus/
I wonder which is the diference, since these adapters have no distances scales, therefore I assumed that both addapters should work for both lenses. I am sure Mr. Kobayashi can´t be wrong... so I wonder which is the explanation for this?

Ernesto

 

[kxl]

https://www.cameraquest.com/NRF-Contax.htm

 

[furcafe]

That explains why you need 2 different adapters for Nikon RF or Contax RF to M mount for accurate RF focusing. The adapters that the OP is asking about don't appear to be RF-coupled (like the old Orion & Cooke & Perkins or modern Amedeo adapters) & are intended to be connected to a VM-E adapter, so it doesn't explain why you would need different adapters for Sony, where you would be focusing through the lens. As stated in the link, it was my understanding that both the Nikon RF & Contax RF lenses are at the same distance from the film/sensor plane at infinity, so any difference between them as far as focus pitch, etc., would not be relevant for TTL focusing. For my A7, I've used the same Amedeo Nikon RF-Leica or Contax RF-Leica adapters w/both Nikon & Contax mount lenses in conjunction w/the CV VM-E close focus adapter without noticeable difference, unlike when using my Leica bodies where I match the adapter to the lens. I don't shoot much at infinity, however, so maybe there is a difference there after all.

https://www.cameraquest.com/NRF-Contax.htm

 

[sevo]

There is a 0.3mm length difference at infinity between Nikon S and Contax mount - so the infinity point would be off.

 

[ernesto]

Thanks! In the link provided by kxl it says that focal length for Nikon is 51,8 vs the 50,0 for Contax. This is a 1.8mm diference. I assume it refers to the infinity focus. So in practical terms considering that the adapter has no coupling nor focusing scale, the adapter intended for Nikon could be used succesfully with a Contax lens, but not the oposite. Nevertheless it would be not comfortable since the Close Adapter helicoid would not stop at infinite, but 1.8 mm further, as pointed by sevo.

Ernesto

 

[sevo]

Nevertheless it would be not comfortable since the Close Adapter helicoid would not stop at infinite, but 1.8 mm further, as pointed by sevo.

It is less than that - according to all sources the flange focal distance seems to differ by about 0.3mm, the rest of the focal length difference ill be accounted for by the lens positioning in the barrel. But that still is enough to account for a difference between about 10m and infinity, so it will not be covered by DOF wide open.