Finished in Sigma’s signature matt-black coating and with an EX gold ring at the front, this is a good looking lens that exhibits excellent mid-aperture sharpness.
Sigma 105mm f/2.8 EX DG Macro
Finished in Sigma‘s signature matt-black coating and with an EX gold ring at the front, this is a good looking lens that exhibits excellent mid-aperture sharpness. There are two settings on the lens to switch between AF and MF modes: one is a short slider close to the lens flange (to activate the AF drive); the other is a forwards/back movement of the focus ring (to disengage the focus ring). It is a potential inconvenience to have to make two settings but the advantage is that the focusing ring does not move, and therefore does not need to be released, when AF mode is selected.
Sadly the AF mechanism is neither quick nor quiet, and was also prone to hunting when tested using an EOS 40D. Fortunately the focus limiter works both at close-range (0.31 – 0.37m) and at non-macro distances (0.4m – infinity). This is useful given that in some macro lenses the focus limiter always includes infinity and only changes the closest available minimum object distance.
The non-macro MTF curve follows a traditional skewed hump profile, with lower resolution wide-open and beyond f/22 sandwiching peak performance (above 0.35 cycles-per-pixel) between f/5.6 and f/11; even at f/16 the resolution remains above 0.3 cycles-per-pixel. An improvised macro MTF test revealed a similar trend at a lower level, in common with other macro lenses.
Although Sigma’s lens works well there is an additional inconvenience beyond the dual AF/MF settings. Specifically, and contrary to the instruction sheet, the supplied lens hood is a screw-in type that cannot be reversed on the lens for storage. (The lens sheet claims that a bayonet hood is supplied but the lens has no lugs to accept a bayonet.)
A further, but minor, confusion may arise from the two differently-located reproduction scales on the lens barrel, which arise from the push-pull movement of the focus ring. More positively, the scales themselves are exceptionally clear and easy to read.
Overall, Sigma’s macro is a useful alternative for a wide range of camera mounts on account of its resolution figures.
The standard skewed curve is seen here with an impressive peak resolution level.