A follow-up to the thread on Summicrons vs Nikkors. Felt bad about getting off topic on the CZJ Sonnar. I have several Nikkor 5cm f2's and 5cm F1.4's, in both S-Mount and LTM. (and seven 50mm Summicrons...none in S-Mount yet...) But there is something about the Zeiss lenses that is "just a bit different". I took some apart and learned that the pre-war and wartime 5cm f1.5 and 5cm f2 CZJ optics modules from Contax mount lenses could be mounted in LTM J-3 and J-8 mounts, respectively. Aperture rings, shims, and variable stand-off rings are compatible. The CZJ Sonnar 5cm F1.5 in a J-3 mount: Collimated for wide-open and close-up: Wide-open at F1.5, on the Canon P: Tight-Crop: Another wide-open, a bit farther away: Tight-crop: Focus with this lens wide-open is good to 100ft or so, best to stop down a little for true infinity. The Contax focal length is slightly longer than what an LTM RF is calibrated for. Compared with the Nikkor, the colors are a bit more muted and the contrast is lower. What you expect from uncoated optics, although this particular lens has a coated front element- aftermarket I'm sure.