Will get a new sample tomorrow
2nd sample .... massive back-focusing ...
Took a quick shot this morning. The focus indicator was way beyond infinity ...
Not that it overly matters for the formal lab test.
Would the minimum focus distance affected as well from that?
Well, I will try to compensate that via AF micro-adjust tonight. Let's see how it goes ...
I believe Canon does not use hard stops at infinity for USM lenses. They claim that focus is reached when you over shoot the focus then back off. Even most MF lenses go beyond infinity. A hard stop at infinity is very nice to have though. My EF 50/1.8 Mark I hard stops at infinity. It is not USM. Neither is the EF 50/1.4 (although it does say ultrasonic on it). I wonder if it has the infinity hard stop?
Focusing beyond infinity makes sense due to thermal effects on the glass.
But not that much.
The 2nd sample isn't really better ...
How much % of new lenses suffer from this centering defect? You hear it quite often, I myself had the same problem years ago with the 70-200mm F/4.0 L (non-IS). I send it to the Canon repair centre, here in the Netherlands and they said it was fine. Which is was most definitely not.
So, how come the experts at Canon just don't see it?