Lens review

Sigma A 105 mm f/1.4 DG HSM

10 July 2018
Arkadiusz Olech

3. Build quality

There is just one lens on the market which could be considered a direct rival of the tested Sigma – the Nikkor AF-S 105 mm f/1.4E ED. That’s why in our chart we also present two other full frame lenses with an entrance pupil of 75 mm but a bit longer focal length plus the Minolta which is a bit slower, aperture-wise, than the Sigma.

You deal here with a huge instrument, that much is clear. The Sigma is not only bigger and heavier than the Nikkor but it is also bigger than the Sigma A 1.8/135, a lens nobody would call small. The filter diameter is also impressive. A complex optical construction certainly has influenced physical dimensions; it is also interesting that both 1.4/105 models feature a worse minimum focusing distance than any of 1.8/135 lenses. Usually that distance increases with the increase of the focal length.

Physical dimensions of the Sigma 1.4/105 can be properly assessed in this photo as we positioned the tested lens between the Sigma A 35 mm f/1.4 DG HSM and the Nikkor AF-S 85 mm f/1.8G.

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Sigma A 105 mm f/1.4 DG HSM - Build quality

The tested lens starts with a metal mount equipped with a gasket. The mount surrounds contacts and a rear element, 31 mm in diameter. The area around that element is nicely matted and blackened. The element itself is mobile – it is situated on the same level as the contacts with the focus set at infinity and when you pass to the minimum focusing distance it hides about 17 mm deep.

Sigma A 105 mm f/1.4 DG HSM - Build quality

The proper body of the lens starts with a smooth, black ring made of metal. It features a white dot, making an alignment with a camera easier, and an inscription “018” indicating the year of the launch.

The next part is a place for attaching a very solid, revolving tripod adapter you get in the box with the lens.

Sigma A 105 mm f/1.4 DG HSM - Build quality

Further on you see the name and parameters of the lens and, above them, there is a window with a distance scale expressed in feet and meters. Below that you find a depth of field scale but it is not especially useful as it features marks only by f/16. On the left side of the scale there is an “A” letter meaning this lens is a part of the “Art” group, an inscription “MADE IN JAPAN” and a focusing mechanism mode switch (AF/MF). You don’t get any autofocus limiter, a feature included in e.g. the Sigma A 135 mm f/1.8 DG HSM model.

Sigma A 105 mm f/1.4 DG HSM - Build quality

The next part is a huge manual focus ring , as wide as 51 mm. Most of its surface is covered by comfortable, rubber ribbing. The ring moves smoothly and is well damped. Running through the whole scale needs a turn through an angle of about 150 degrees – a sensible value for an autofocus construction.

Sigma A 105 mm f/1.4 DG HSM - Build quality

Right behind the manual focus ring the diameter of the lens increases sharply and in that part you can find a hood mount. It goes round a non-rotating filter thread, 105 mm in diameter, and that thread surrounds a front element, as big as 91 mm in diameter.

Sigma A 105 mm f/1.4 DG HSM - Build quality

The design of the lens consists of 17 elements positioned in 12 groups. By including three FLD glass elements and two SLD glass elements the optical system is supposed to minimize chromatic aberrations. Additionally one aspherical lens element is positioned the closest to the detector. Inside you can also find a rounded aperture with nine diaphragm blades which can be closed down to a value of f/16 at the maximum.

It’s worth adding that the front element of the lens is covered by oleophobic and hydrophobic coatings which make cleaning easier and limit smudging. Additionally the Sigma A 105 mm f/1.4 DG HSM is compatible with the Sigma USB Dock station which allows you to calibrate autofocus, update software and create personal settings profiles.

Buyers get in the box both caps, a hood made of carbon fiber reinforced plastic (CFRP), a solid and removable tripod adapter, a hard case and two straps, one for the lens and one for the case. Additionally, you get a rubber cover for the tripod socket to secure the place after removing the tripod adapter.

Sigma A 105 mm f/1.4 DG HSM - Build quality

Sigma A 105 mm f/1.4 DG HSM - Build quality