Quote Originally Posted by lxdude View Post
Where'd you find that out? I'm always interested in having any misconceptions of mine corrected.
The PentaxForums.com has great info on older lenses. There were two versions of the M42 28mm f/3.5 lens before the SMC, both slightly different, but 7 elements in 6 groups. The S-M-C version was actually different, being smaller all around, 7 elements in 7 groups.

The K version was changed again, being 8 elements in 7 groups, growing a bit in size from the M42 ones.

The SMC-M one changed again, being 5 elements in 5 groups, and shrunk back down to accomadate the standardized 49mm filter thread. Definitely not as sharp as the K series.

I think out of all the lenses I've owned, there was the most variation of the 28mm f/3.5 from it's beginnings as the massive 58mm front Super Takumar, through the smaller Super Takumar, S-M-C Takumar, SMC, and SMC-M. It was changed fairly significantly with each generation.

I think the K one is the sharpest of them all, and I believe it's generally regarded as the best of that lens by most.