The Mamiya Sekor SX 3.5/20mm has a somehow unusual optical construction which reminds of the early Nikkor 200mm 1:4. At infinity, and using a 24 MP FF camera, its performance is surprinsingly good, and certainly much better than the (older) Nikkor mentioned. The lens focuses down to 2.3 m - not really overwhelming, especially in relation to the 80-200mm zooms which would soon overtake the market and make the 2.8/135mm and 4/200mm teles obsolete.

The Sekor SX 3.5/200mm has a pretty good resolution wide open, certainly comparable to the more common 4/200mm [5/5] designs of its time. Only the CAs are bit stronger than with the best 4/200mm lenses of its time (e. g. the Minolta MC/MD 4/200mm Var I).