Pros:Sharp sharp sharp; manual adjustment for autofocus; great contrast, color.
Cons:Have to back up a long way for portraits and regular shots.
The Bottom Line: Make this your first prime lens. Open up the whole world of seeing and shooting close-in subjects.
You've heard "sharpness" tossed around, and you may think you know what that means. But unless you've been shooting with L-series lenses, you'll see so much more detail than before, you'll have a whole new appreciation for a "sharp" picture.
Recommend this product?
Ever notice in Photoshop that when you blow up a photo to 100%, the smallest pixels tend to fuzz together? This effect is more pronounced with more megapixels, so a 12-megapixel photo may not have much more usable detail than a 6-megapixel one. Well, the EM 100mm f/2.8 USM lens will preserve 12 megapixels worth of detail.
This is my first fixed lens. Not having to zoom saves time. Not having a zoom forces some advance planning, and requires walking around to get the right distance from the subject (especially for portrait shots or anything other than up close). It's exercise for the mind and the body! :-) Practicing with prime lenses will make you a better photographer.
I also have the Canon 70-300mm USM zoom lens with a 1.4x teleconverter, which is what I use for shooting wildlife. By happy coincidence, this combination at widest angle is almost exactly the same field of view as the 100mm macro lens. So before getting the macro, I practiced using the long lens unzoomed for portraits and outdoor shots, to get a feel for the field of view. There's no comparison for close-up shots, because with the zoom lens you have to back up about 6 feet to focus properly on a flower, while with the macro lens you can practically tickle the petals.
The view from so close in, with so much detail and such shallow depth of field, is almost otherworldly. A single flower, whether it's deep in the woods or next to your driveway, can become a work of art. You'll learn more about insect body parts than maybe you wanted to know.
The shallow depth of field is a blessing and a curse. The biggest problem I have with true macro shots is that sometimes it's difficult to get two almost side-by-side blossoms both in focus at the same time. You'll learn more about aperture priority than you knew before.
In such situations, you'll typically use manual focus, to choose which spot is more important if you can't focus equally on both. But the autofocus is very good too. There's even the option of making tiny manual focus adjustments while it's autofocusing. (Although it feels a bit like you're fighting with the lens.)
If you want to use this lens to take a picture of both the flower and the whole planter or garden bed, you might have to back up a long ways for the long shot, and maybe even run out of room. I am in the habit of carrying both a 20D with big zoom and a smaller camera for wide-angle shots when I go hiking. With this lens, I apply the same strategy (20D with macro lens plus S3 IS or something for wide shots) when strolling through the woods or botanical gardens.
The sharpness also makes this a great lens for photographing (small) documents, such as postcards or old photographs, instead of scanning them. If you use this technique watch out for the texture -- the lens will pick up any grain from the paper, reflection from the finish, and highlight any curvature in an old photo, which may lend more realism than you're looking for.
I've sometimes questioned whether Canon was too aggressive in toning down the default sharpening, contrast, etc. for their prosumer cameras, as I usually have to apply some sharpening, saturation, contrast, etc. to every picture from the 20D. But those defaults are really to accomodate lenses like the EF 100mm f/2.8 USM macro, because those shots come out of the camera with enough sharpness, color, and contrast to use without any Photoshop steps.