No other lens is made for a more specific task than the macro lens. The Sigma 105mm F2.8 EX DG Macro is indeed made for one thing in mind. Allowing the user to capture 1:1 magnification which also gives it the name “Macro”.

Sigma makes quite a number of macro lenses and this is their third in terms of focal length. Being 105mm it´s not only suited for flowers but will give the user the ability to get closer to insects as well. Granted a 180mm lens (which Sigma also makes) would be a better choice for insects but this 105mm gives you a bit of everything.

One of the things that makes a macro lens interesting is the ability to get close to your subject. – Real close up to a 1:1 magnification for it to be a true macro lens. The Sigma 105mm F2.8 EX DG Macro delivers just that with a sharp and beautiful result.

As you can see the ability to get real close opens a new world in terms of photography.
Both taken with the same lens although the left one would resemble the typical nearest focus ability of a similar sized non-macro lens.

The area in focus (DOF or depth of field) as you might have noticed becomes very thin when getting close. With a longer focal length as The Sigma 180mm F3.5 EX Macro lens the DOF would have been even smaller due the an angle change on the subject.
In your typical situation you want to use a small aperture to get the deepest DOF. – That does require the user to use a tripod and is highly recommendable. The shots above was take af F2.8 which is the largest aperture

The Sigma 105mm F2.8 EX DG Macro  is a very sharp lens even at widest aperture.
The image of the left has been post processed while the 100% crop on the right hasn´t

As per standard of close to all macro lenses they are optimized for close focusing and optical perfection. The Sigma 105mm F2.8 EX DG Macro isn´t any different here. The lens is virtually distortion and vignetting free. And it´s sharp wide open (F2.8) – Stopping down to F6.3 increases the sharpness slightly but in any real world situation you´ll have to look for differences to see them. Despite the “portrait” focal length the Sigma 105mm F2.8 EX DG Macro adds a creative perspective if you´re forcing yourself to shoot landscapes.

Two very different shots both taken at the 105mm. The focal length makes the perspective seem narrower and
forces you to think a bit different if shooting landscapes.

The Sigma 105mm F2.8 EX DG Macro has a selectable focus range button. You can select from two options. “Limit” and “Full”. With the Limit option selected you force the lens to focus either from 0.313 to 0.39 meters or from 0.4 meters to infinity. It´s nothing advanced but is a nice feature.

On the Canon version which I´m using you have to switch two functions in order to disable the auto focus motor. One being the typical AF or M button and the other is pull the focus ring downwards and you have to do this in this very order. Quite a odd and cumbersome solution. Why not just have one or the other..
The auto focus on the  Sigma 105mm F2.8 EX DG Macro is, despite using a pro-body, very slow. It´s not a lens you´ll be using in AI-Servo or similar focus mode. But then again with the big focus ring and intended subjects to photograph there´s a good chance you´ll be using manual focus either way. It´s way faster and is often required when shooting macro. Fair to say the auto focus is precise on every focus range.
Another important thing and often spoken of as a major reason to buy a larger size aperture lens is the bokeh.

The bokeh is butter smooth on the Sigma 105mm F2.8 EX DG Macro. Not unsurprisingly especially at F2.8

Downloadable samples (Right click as choose “save as..”)
Sample 1
Sample 2

Conclusion
As you might know by now I´m quite fond of the Sigma 105mm F2.8 EX DG Macro. Its relatively versatile focal length suits most photographers and it delivers a sharp and usable result a F2.8 improving slightly stopping down. The focus motor isn´t the fastest on the block but it´s precise. No doubt about using manual focus is the better option.
Overall a great lens for everyone looking to do 1:1 magnification macro photography.