It usually goes without saying that a zoom lens won't come close to matching the performance of a good prime (non-zoom) lens at any given focal length. But is that always the case? When we tested the non-IS version of this lens, we were mightily impressed with its image quality across the board. The new IS (Image Stabilized) version of it is at least as good, prompting senior tech Jim Tanner to look into just how it did stack up against excellent primes at various focal lengths. The results may surprise a lot of readers, but I'll let you read for yourself what Jim found. We also took an informal look at the strength of its IS system, and found that it does seem to live up to Canon's claims of 4 stops(!) of improvement in shake reduction. All in all, a tremendously impressive lens, read on