'Pentax-K' vs Pentax-M 50/1.4

[caspert79]

I have a question regarding the 'Pentax-K' (52mm diam) 50/1.4 vs Pentax-M 50/1.4 (49mm diam).
It's clear that mechanically, these lenses are different. What about their optics: do they share exactly the same glass?

[CarbonR]

If you look at BDimitrov, no. The K has the same layout than the Takumar, the M is a new formula

[caspert79]

Thanx!

[keyser1884]

From what i understand, the Takumar and 'K' used identical formulas. The 'M' lens had it's own formula and the 'A' lens through to the 'FA' lens of today share an optical formula. The only thing that has changed since the early 80's are the casing (change to AF) and lens coatings.