Lens review

Sigma A 70 mm f/2.8 DG Macro

30 June 2018
Arkadiusz Olech

3. Build quality

The following chart presents a comparison between basic parameters of the tested lens and those of its predecessor and other full frame f/2.8 rivals with similar focal lengths.

The new Sigma is an instrument optically more complex than its predecessor but it is also physically lighter. When it comes to dimensions the new model is slimmer but longer. The Micro Nikkor is handier at every aspect for a change – but it has a bit shorter focal length and a simpler optical system.

In the photo below the Sigma A 70 mm f/2.8 DG Macro is positioned between the Canon EF 100 mm f/2.8L Macro USM IS and the Sigma A 35 mm f/1.4 DG HSM.

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Sigma A 70 mm f/2.8 DG Macro - Build quality

The tested lens starts with a metal mount surrounding contacts and a black, matt, slightly ribbed inner tube. Inside that tube, about 1.5 cm deep, you can find a rear element which doesn’t move and is 27 mm in diameter. From that side everything seems to be in perfect order – you get a sealed construction without any slits and/or visible electronic parts, everything is properly darkened and matted.

Sigma A 70 mm f/2.8 DG Macro - Build quality

The proper body of the lens starts with a smooth, black, metal ring on which there is a white dot, making an alignment with a camera easier, and an inscription ‘018’ indicating the year of the launch. That ring turns smoothly into another matt part of the barrel which features the name of the lens, its basic parameters, the A sign, meaning you deal here with an Art category instrument, an inscription ‘MADE IN JAPAN’ and two switches. The first of them (AF/MF) allows you to choose the focusing mechanism working mode and the second one is a focus limiter with three options available: FULL, 0.258–0.5 of a meter and from 0.5 of a meter to infinity.

Sigma A 70 mm f/2.8 DG Macro - Build quality

Further on you see a manual focus ring, 50 mm wide, most of its surface covered by ribs. There is no distance or depth-of-field scale. The ring is a fly-by-wire construction and turning through the whole distance scale takes an angle of over 750 degrees – it is a huge value, enabling very precise settings.

Sigma A 70 mm f/2.8 DG Macro - Build quality

Behind the manual focus ring you see a small fragment of the casing with the hood mount.

When it comes to macro lenses, lately the producers have been opting for closed constructions which don’t change their dimensions when you pass to 1:1 reproduction ratio. The new Sigma, like its predecessor, is an exception to that rule. The front element, 23 mm in diameter, is surrounded by a ribbed tube and a non-rotating filter thread, 49 mm in diameter. At the same time the front element recesses into the tube by almost 3 cm. Still when you pass to the minimum focusing distance the whole system extends forward and the extending barrel is made of plastic. The dimension of the lens can increase by as much as 51 mm. When you take photos in 1:1 magnification, the rim of the tube surrounding the front element is situated about 5 cm from the photographed object.

Sigma A 70 mm f/2.8 DG Macro - Build quality

The optical construction consists of 13 elements positioned in 10 groups. Among them you can find two low dispersion elements with properties similar to fluorite (FLD), two others are classic low dispersion SLD elements and there is also one aspherical element too. Inside there is also a round aperture with nine diaphragm blades which can be closed to a value of f/22 at the maximum.

It’s worth adding that the Sigma A 70 mm f/2.8 DG Macro is compatible with the Sigma USB Dock station which allows you to calibrate the autofocus, update software, and create your own personal setting profiles.

Buyers get both caps, a hood and a hard case in the box with the lens.

Sigma A 70 mm f/2.8 DG Macro - Build quality