I had assumed the K and S-M-C were the same, but I recently found out that the K 28mm f/3.5 was a totally new design. The K 28mm f/3.5 is definitely sharper than the 2.8 versions, and both seem to be better than the M42 versions.
Where'd you find that out? I'm always interested in having any misconceptions of mine corrected.
I do use a digital device in my photographic pursuits when necessary.
When someone rags on me for using film, I use a middle digit, upraised.