Friends, I bought a Contax to Leica adapter to mate the 645 lenses to my S 006. As I researched the options I did so on the assumption that the field of view extrapolation would be the same for both product lines. In other words, that I could use the 0.8 magnification factor to estimate the field of view in full frame terms. I think of my 70mm Summarit S as the rough equivalent of a 56mm in full frame terms. And I assumed that I could do the same math for the Contax lenses.

But I read the core thread on this site that discussed the merits of the Contax lenses mated to the S. In the course of the discussion, at least two posters suggested that the reverse was actually true. That the stated focal length of the Contax lenses are 1.25x longer than the lens length on the S body given the fact that the S sensor is smaller than the 645 format.

As posted:

Well, how the edges are doesn't really matter. The Leica S chip is 30x45mm, so it will never see the edges of any of these lenses.

The 35 becomes a 43 (x1.25)

If this is so, then the 80mm would be a 100mm, the 120mm would be the equivalent of a 150mm.

I have not seen this discussed directly in any thread and would be obliged if someone could help lift the veil. I need to know if one of these lenses is going to have a field of view that, in full frame terms, would be 20% shorter or 25% longer than the stated focal length.

On another note, I am committed to the 120mm makro and 80mm for its unique signature, but am dithering on the short end - either the 45mm or the 55mm. Any thoughts would be most helpful.

Obliged for the help.

David