Over the decades, I have briefly owned a couple of Yashicamats with the 75mm 3.5 taking lens. At one point, I did on film resolution test comparisons of five different TLRs, including the new in the box Yashicamat. All mounted some version of a Tessar-copy 4-element taking lens. My test conclusions were:
1. Thee Yashinon lens used on the first Yashicamat is the same as used on the last over a 26 year period. Lens coatings may have been altered over time, but the on film performance is basically identical.
2. The Yashinon lens was the poorest performer of them all, and by a significant degree. The best was the Minolta Autocord, followed closely by two different Zeiss Tessars in Rolleiflex and Rolleicord, Ricoh Diacord, and way down there, the Yashicamat.
3. The Yashinon is quit poor wide open, but improves significantly as closed down. At 5.6 to 11.0, it is quite respectable, nearly equal to others.
4. With most prints today made by scanning and inkjet printing in smaller enlargements, the differences among these lenses is made insignificant by the digital processing. Making a traditional wet print larger than 11x14 inches might show a difference under critical examination.