A year ago Canon unveiled an upgraded version of one of its crown jewels: the 70–200mm f/2.8L IS lens. The original, debuting nearly 10 years ago as one of the first f/2.8 lenses with IS, was fast, plus sharp at the wider focal lengths. It was heavy, though, and at $1,700 (street), expensive. And here’s Version II, even heavier and even more expensive ($2,300, street). What’s up with that?