Quote Originally Posted by Richard Jepsen View Post
An old Elmar 50mm f/3.5 has lower performance at wider apertures since it is 4 elements in 3 groups. The sweet spot for the Elmar f/3.5 is f/8 vs f/4 for the Cron...
Elmar ƒ/3,5 stopped 1 or 2 stops performs the best, ƒ/8 is not what Elmar was optimized for.
Even on the uncoated Elmar ƒ/3,5 LTM., the R index is above ƒ/6,3 - that's 2 stops from wide open.
ƒ/8 is the stop, where all lenses performs equally bad.
Larger DOF with prime lens does not mean best optical performance or sweet spot, unless You want Your shoes ends and infinity to be in focus.