Summary

There is much to like about the Sigma 105mm Macro EX DG for Four Thirds. It feels solidly built and is positive in handling and results. It's also a very versatile lens, useful for portraits and medium telephoto work, especially in low light, as well as macro work. The Sigma 105 Macro is more effective as a macro lens than the more expensive Olympus Digital Zuiko 50mm f/2.0 Macro, which only goes to 1:2 reproduction, though optically the Olympus lens has the edge. You can get similar 1:1 macro reproduction to the Sigma 105 with the considerably cheaper, smaller and lighter Olympus Digital Zuiko 35mm f/3.5 Macro, though this is slower, less robustly constructed and arguably less versatile as a general purpose lens. Sigma's manual/auto focus mode switching takes some getting used to, but the mechanical manual focus actually works very well. In auto focus, Sigma hasn't endowed this lens with its HSM sonic motor system, so the focus action is not particularly fast or refined. I've noted mixed feelings about the finish of the Sigma 105; the matt finish seems to be hard wearing, but isn't as attractive as the traditional semi-shiny finish found on many other lenses.

What we like:

True 1:1 macro reproduction
Focal length versatility
f/2.8 maximum aperture good for low light focus
Good overall optical performance
Solid construction
Low distortion throughout the focus range, including macro
Good manual focus feel
Focus limiter to help reduce out of focus hunting
Good value

What we don't like:

Matt black style of external finish
Lens hood is screw fit instead of bayonet (contrary to user guide)
AF not as impressive as sonic motor powered lenses
Three adjustments needed to switch between manual and auto focus
Mechanical rather than fly by wire focus means no AF+manual focus mode or focus direction choice
Would like to see a weather sealed-version of this lens