The leica contax adapter is built with leica quality. Locks, stable and works.
The image above is with a 55mm contax and focuses faster than the contax 645, is way too sharp, but then again ultra sharpness doesn't concern me. The difference between leica and contax lenses are the roll off, not the sharpness.
Leica lenses roll off smooth, contax zeiss a quick roll off in tone, Leica smooth, almost old schneider smooth, but sharp when you need it.
I picked up some purple ca on this image, kind of liked it, though could have fixed it in processing. Understand i have the first S2 with a ccd that I love and I pushed the hell out of this image mixing tungsten and daylight, so no color is meant to be technically perfect, because to me technically perfect is boring.
Still, your contax lenses will be fine, but at the end of the day, save your cash cause your gonna buy some leica glass (even though you don't need it) because . . . well it's leica glass and leica glass like leica cameras are way cool.
IMO
BC
I don't have sharpness as my main concern either (as long as there is enough of it), without having ever tried a Leica S, I see an opportunity to get rid of my Nikon DSLRs altogether, thus considerably restricting the equipment I have to carry, I don't plan to stop using my Contax system either, since the main use of the two backs I now use on it is in multishot mode (a feature I can't have with the Leica), so I would like your (or other that can contribute) advise on the following planning I have in my mind:
I now use my CF-39MS back for MF in single shot and I do find the quality to be fine but with higher ISO (which sometimes I need) so I keep two FF Nikons as well... Recently, I got the JAS adapter to use my C645 lenses on the Nikons and got rid of all my Nikon glass but the 17-35/2.8 (to have for wide angles), the old 35-70/2.8 (which was cheap to sell and nice walk around lens) and the 85/2.8 micro PC which I need for product photography, I also have a five lens (from 65 to 210) FUJI GX-680 system on which I have an extremely accurately made MF back adapter plate which directly takes Contax mount backs on it and thus, I'm able to use both my backs on the Fuji (in multishot mode too) for whenever I need movements. What I want to do, is to restrict the equipment further, yet not to reduce the functionality I now have with my system.
My thinking is that it would be pointless to look for a CCD Leica S, as it won't add anything that I can't do with my CF-39MS back on Contax (is that so?) but will only reduce the bulk, but the S-007 does give me the higher ISO quality I now use the Nikons for... OTH, I also have a concern because I will also have to replace the Nikkor 85PC which is much of the use I do on my DSLRs, with a (very expensive) respective Leica lens (the 120?)... and of course add the 24mm Leica to go wider...
Here is my questions then...
1. Am I right to think that the Contax 45mm will perform great on the Leica because of the crop factor that will improve its performance on the edges of the frame?
2. Am I right to think that the (problematic) close focusing distance of the Contax 140 won't be an issue on the Leica because one will have to add distance between him and the subject?
3. Am I right to think that the Contax 35 will have much reduced distortion?
4. Am I right to think that the 80mm will also have improved performance at wider apertures because of the crop frame?
5. Am I right to think that the 45-90 vario will be great if used wide open?
P.S. Mind you that my Contax system is huge (four bodies, all glass & the mutar 1.4x but the 350 lens, all screens, 13 & 26mm extension rings, all finders and right angle attachment too)