SMC Pentax 85mm f/1.8 (K mount)
Pentax Super Program with cable release and, for f/8 to f/1.8 only, depth of field preview button held in to reduce automatic diaphragm vibration.
Vignetting = B @ f/1.8, A- @ f/2.8, A elsewise
Distortion = slight pincushion
Aperture Center Corner
f/1.8    C+     B-
f/2.8    B+     B
f/4      A-     A-
f/5.6    A      A
f/8      A      A
f/11     A      A
f/16     A+     A-
f/22     B+     B
Notes: 1st version of the 85mm in a K mount. Moderately high contrast from f/2.8 to f/16, moderate contrast elsewise.