tooffy
Established
Tooffy- yours looks like it was optimized for use wide-open. I changed the shim on mine, added 0.1mm, to use at F1.5. Before that, it was best at F4 and compared poorly against the Nikkor-S 5cm F1.4. My personal opinion is that Canon optimized it for use stopped down, and that is why it never got the fame of the Nikon Sonnar.
Hi Brian,
I'm not sure but I almost always use it wide open at about closest focusing distance and the photos turn out very good.
I'm sure glad that mine turns out that way! 🙂