SMC 35/2 at 1.5 m focus distance

f 1:2

f 1:2.8

f 1:4

f 1:5.6
f 1:8

f 1:11

There's noticeable light fall-off in corners wide open even in this
kind of composition. Bokeh is slightly double-imaged wide open in
background. Background bokeh becomes good at f 1:2.8, and excellent
at f 1:4 or closer.