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Lens review

Sigma A 40 mm f/1.4 DG HSM

10 December 2018
Maciej Latałło

3. Build quality

The following chart shows a comparison of basic parameters of the tested Sigma and other full frame models providing a similar angle of view. We have an impression that, no matter what you put into this chart, the Sigma A 1.4/40 still will remain a massive, bulky, and heavy instrument. It should be noticed that the 35 mm and the 50 mm devices from the Art series were considered optically complex, consisting of 13 elements. The new model features as many as 16 elements, imagine that.

The photo below emphasizes the physical dimensions of the Sigma A 40 mm f/1.4 DG HSM. Even the quite significant Sigma A 35 mm f/1.4 DG HSM looks shapely and small next to it. The classic gauss 1.4/50 Sony device, which construction comes directly from the Minolta reflex camera system, seems to be designed for a detector at least two times smaller even if it is a lens dedicated for full frame.

Sigma A 40 mm f/1.4 DG HSM - Build quality

The tested lens starts with a metal mount which surrounds contacts and a rear element, 32 mm in diameter. That element doesn’t move and is situated on the same level as the mount with the lens set at infinity; when you pass to the minimum focusing distance it hides inside about 1 cm deep. By doing so it reveals the interior of the tube, well matted and ribbed, without any slits. The front element doesn’t move for a change – it means that during focusing the optical system changes along with the focal length of the lens.

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Sigma A 40 mm f/1.4 DG HSM - Build quality

The proper body of the lens starts with a smooth, black, metal ring on which you can see a white dot making an alignment with a camera easier. Then there is an ‘018’ inscription meaning the year of the launch.

Sigma A 40 mm f/1.4 DG HSM - Build quality

Further on, you find the name and parameters of the lens and above them a window with a distance scale expressed in feet and meters. Below the window you get a depth of field scale but with just two aperture markings, for f/8 and f/16, so moderately useful. On the left side of the scale there is an ‘A’ letter meaning the lens is classified as an ‘Art’ device, then an inscription “MADE IN JAPAN” and a focusing mechanism mode switch (AF/MF).

Sigma A 40 mm f/1.4 DG HSM - Build quality

Next you see a very big, 56 mm wide, manual focus ring. Most of its surface is covered by rubberized ribbing. The ring moves smoothly and is properly damped; running through the whole distance range takes a turn through an angle of about 110 degrees. It is a sensible value but still several dozen degrees shy of an angle of rotation which would guarantee the utmost precision.

Sigma A 40 mm f/1.4 DG HSM - Build quality

Right behind the manual focus ring there is a hood mount. The mount is surrounded by a non-rotating filter thread, 82 mm in diameter, and the thread goes around the front element which doesn’t move and is 70 mm in diameter so over 20 mm bigger than the front element of the Sigma A 1.4/35.

The optical construction diagram is really impressive, just have a look at the picture below.

Sigma A 40 mm f/1.4 DG HSM - Build quality

Inside you can find as many as 16 elements positioned in 12 groups; three of them are made of low dispersion glass with properties similar to fluorite (FLD), three others are Special Low Dispersion SLD elements and there is one aspherical element too. The lens also features a round aperture with nine diaphragm blades which can be closed down to a value of f/16 at the maximum.

Buyers get both caps, a padded case with a strap, and a petal-type hood in the box with the lens. The hood is very original for a Sigma, it consists of two parts, the classic plastic one, similar to other hoods of this producer, and the rubber one, situated closer to the mount. I don’t completely grasp the reason behind such a construction which, in my opinion, spoils the esthetics of the lens. The rubber part catches dirt and dust easily; it looks a bit shabby even right after taking it out of the box.

Sigma A 40 mm f/1.4 DG HSM - Build quality