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Lens review

2010-05-05
 

Sigma 105 mm f/2.8 EX DG Macro

3. Build quality

The Sigma’s 2.8/105 casing seems to be solid and massive. This impression is strengthened by the front element, hidden deeply in a dark, threaded material. You can choose the mount versions, which is of course made of metal, from those appropriate for Canon, Konica-Minolta, Nikon, Pentax and Sigma.

Sigma 105 mm f/2.8 EX DG Macro - Build quality

Although this lens is quite fast and it features a 105 mm aperture it is not much bigger than the „kit” 18-55 mm Canon lens. It can be clearly compared looking at the picture below.

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Sigma 105 mm f/2.8 EX DG Macro - Build quality

When it comes to the inner construction, the Sigma is very complex for a prime lens. It consists of 11 elements in 10 groups. All the elements are made of ordinary glass so we can’t find any low-dispersion or aspherical pieces in this case.

Sigma 105 mm f/2.8 EX DG Macro - Build quality

The aperture range of the Sigma 2.8/105 is an interesting property. In the case of lenses with mounts for Canon, Konica-Minolta and Sigma cameras you can stop it down to the f/45 aperture. The company justifies it by saying that they wanted to make a very deep depth of field available. It seems to us only a marketing gadget, though, because a lens stopped down to f/45 has less than 15 lpmm resolution so it can hardly be of any use.

The tested lens is marked by the “Macro” symbol – it means that it is designed to shoot photos from close distance. As a matter of fact the Sigma can take sharp pictures already from 31.3 cm with 1:1 magnification.

A comfortable manual focus ring can be moved up or down and it has two positions marked as MF and AF (so-called Dual Focus mechanism). In the MF position we can use a big and handy ring which allows us to set the needed focus precisely. On switching to AF that comfortable ring stops rotating so the lens can still be held comfortably.

The lens is equipped with an aperture with eight diaphragm blades which is supposed to ensure a pleasant background and nice bokeh.

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