BTW...I was playing with the Sigma 85A compared to the new lens yesterday. One thing that impressed me was how well (not perfect but ballpark) the Sigma MTF matched with what lensrentals observed:

85A Geometrical MTF



Sigma MTFs explained (v different from Canon)
https://www.sigmaphoto.com/lenses/le...tf-chart-guide


LensRentals measured MTF
Olaf Optical Testing, 2017


So, comparing the two red lines (both 10 lp/mm wide open) and the two green lines (both 30 lp/mm wide open), some serious similarities. If anything, the lens tested better than the MTF would have indicated.

I checked out the 50A, and the same generally appeared to be true. Nice to see some MTFs validated.