Please forgive us but for obvious reasons we've reused some portions of the corresponding full format review of this lens.

The Canon EF 100mm f/2.8 USM L IS macro is the 6th macro lens in the Canon EF lens lineup. It's a full format lens but you can naturally also use it on your APS-C DSLR where its field-of-view is equivalent to about 160mm in classic terms. The lens does not replace the highly popular EF 100mm f/2.8 USM macro but is meant as a higher quality option featuring Canon's proven lens-based IS (Image Stabilizer). Just like most IS lenses the design complexity increased quite a bit from only 12 elements in 8 groups in the "conventional" macro lens to 15 elements in 12 group. In theory this does allow a higher degree of corrections but you also risk more flare in contra light situation.

The build quality is excellent but then we've expected no less from a professional grade "L class" lens. The lens body is made of very high quality plastics and a metal mount. The broad rubberized focus ring works very smooth. Similar to the non-L macro lens it features a "true" inner focusing system so the lens does not extend when focusing towards closer focus distances. The Canon EF extension tubes are supported whereas the EF tele converters cannot be used.

It took Canon quite a while to release their first macro lens featuring an image stabilizer. Nikon won the race here although their VR is not all that efficient in macro situations. The Canon lens feature a new "hybrid" IS which does not only compensate "conventional" shake but also linear movements. Canon claims an efficiency of 2 f-stops at 1:1 magnification and 4 f-stops at standard focus distances. These extremes seem to be a little optimistic but they may work out at times (and if you skip your coffee). Whether it makes sense to take macro images at 1:1 magnification with activated AF and IS is a different story. The depth-of-field is so shallow here that shake due to "free hand" shooting is just one of your problems. However, the IS is also able to handle tripod-induced shake so it does certainly make sense in this scope. The IS efficiency at more conventional focus distance remains unchallenged by these thoughts of course.

The AF is based on the usual ultrasonic motor (USM) which is both very fast and virtually silent. Nonetheless Canon provides a three step focus limiter in order to avoid AF hunting throughout the range which can be a problem when using AF in macro situations. During our field tests the AF accuracy was excellent. The performance in contrast AF mode (aka LiveView) was also decent(both on the 5D II and 50D). That all said - many macro photographers do still prefer manual focusing simply because it's easier to fine-tune a specific spot.

Here's a spec comparison between the existing and this new 100mm macro lens: