Canon 100mm f/2
But wait: the 100mm f/2 has no IS, but it’s two stops faster than the f/4 L lens that costs over twice as much and isn’t quite as sharp. 1/60 at f/2 is the same as 1/15 at f/4, the fastest f/stop of the 70-200mm f/4 IS at 100mm, or only a one-stop advantage for the IS lens.
Since the 5D Mark II sees more blur due to its higher resolution, I’ll take away a half stop, leaving this f/2 lens only about a half-stop behind the excellent hand-holdability of the 70-200mm f/4 IS for still subjects.
If the subject is moving, this 100mm f/2 is better because the extra two stops of real speed lets you use a shutter speed four times faster to stop the action.
The 70-200mm f/4 IS is better for images of still subjects in the dark because it gives you deeper depth-of-field, using f/4 at a slower speed versus f/2 at a faster speed.
