There were 2 Yashica 50mm F1.4 lens productions, one each by Yashica Tomioka and the Yashica Group. This matters because the Tomioka version used the Biotar/Xenon 7 element enhanced rear (2) element type while the Yashica Group used a Ultron 7 element enhanced rear group (4) element type. 2 unique and different designs.
BTW, The first Takumar was an 8 element design and soon thereafter changed to the above Ultron design which Pentax kept through the K mounts. This first 8 element design required a glued triplet making it cost prohibitive so it was replaced by a better design.
Biotar/Xenon type included, Vivitar, Chinon, Tomioka, Mamiya Sekor, Cosina, Canon FL 58 1.2, Summarex 85 1.5, Nikkor-S 55 1.2, and the Zeiss Pancolar and Planar (Berger) 55 1.4’s.
The Ultron type included, Zeiss Planar (Glatzel) 1.4 and 1.7, Takumar 1.4, Pentax A 1.2, Pentax SMC 85 1.4, Canon EF 1.4, Tomioka and Yashica 1.2, Zenitar 1.4, Fujinon 1.4, Porst 1.2.
I think by following the lenses that fall under each design a sense can be realized that the Ultron added high speed performance with superior sharpness as many of these lenses are some of the sharpest ever in manual focus. A good reference to illustrate this is comparing the Canon EF USM wide open performance to any Biotar/Xenon wide open, they just won’t compare performance wise as the Canon is a pinnacle for wide-open sharpness achievement in lens history only equaled by a Leica Summicron.
Just because they might appear as similar doesn’t necessarily make it all so? Looks can be deceiving. The Biotar/Xenon design uses 2 elements in the rear group while the Ulton uses 4 elements in the rear group…..none of these above were assymetric Planar designs like the old Zeiss Biotar, Pentacon, Meyer Optik, Helios, Schneider Xenon. Pancolar types……