Things to keep in mind when reading various review.
1. There is no such a thing as free lunch. Anyone who claims fast autofocus with this combo is smoking something. Canon white papers claims a 75% reduction in autofocus speed. It will also degrade image quality, no matter what lens you put it on.
2. As for Image quality, acceptability, and degradation, there are several factors in play. Of course where you end depends on where you start. used on an optically superb lens, after some image degradation, you can still end up with good image quality. with mediocre lens, you end up with bad, and with a bad lens, you end up with mush. The other factor in acceptability is the… Read more