The following chart presents a comparison between basic parameters of the new Sigma, its reflex camera predecessor, and other 1.4/50 class instruments designed for full frame mirrorless cameras.
The new Sigma, along with the Sony GM, sticks out with the most complex optical system. What's important, despite a high number of elements inside, the producers managed to keep the weight and physical dimensions in check. As a result, the new model is significantly lighter than its predecessor and also lenses produced by Panasonic and Zeiss. Of course it doesn't change the fact that both the new versions of the Samyang and the Sony GM managed to do an even better job in this area.
In the photo above the Sigma A 50 mm f/1.4 DG DN is stacked up against its direct brand name rival, the Sony FE 50 mm f/1.4 GM. We also included an older, double gauss construction in form of the Canon EF 50 mm f/1.4 USM for the comparison's sake.
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The tested lens starts with a metal mount that surrounds contacts and a rear element, 28 mm in diameter, that doesn't move. The element is hidden inside a well-blackened, ribbed tube less than 1 cm deep. It is also surrounded by a black 29×23 mm frame.
A black ring made of metal that increases its diameter very quickly is the first part of the proper barrel. The ring features a white dot, making an alignment with a camera easier, and the model year of the instrument, in this case 023, information that the lens was made in Japan, and an inscription with the focusing mechanism working range :”0.45M/1.45FEET– ∞”.
Further on you see an aperture ring, 12 mm wide, mostly covered by ribbing; it features aperture marks ranging from f/16 to f/1.4 and an A value (meaning automatic settings). The ring moves every 1/3 EV stop but you can also make it clickless. Its performance is very comfortable and smooth, simply beyond reproach.
Further on you see an immobile part of the lens covered by plastics with the logotype of the company, the name and parameters of the lens, its serial number, some fine ribbing, an 'A' letter that means the instrument is qualitifed as an Art line lens, and a whole array of switches. The first of them – AF/MF FOCUS– allows you to control the focusing mechanism working mode. The second one – AFL – recalls a specific autofocus position but you can allot it other functions too. Below there is a CLICK OFF/ON switch that controls the aperture ring mode. On the other side you can also find the aperture ring lock switch that can be set either on the A position or at any other point ranging from f/1.4 to f/16.
A manual focus ring, as wide as 49 mm and mostly covered by ribbing, is another part of the barrel of the lens. It is a focus-by-wire mechanism; you won't find any distance or DOF scale on it. Its performance we found very smooth and the ring remains properly damped at the same time. Its focus throw depends on the speed of your turning. When you move the ring faster it amounts to approximately 200 degrees, when you turn it slower you can reach even over 400 degrees. Both these are values allow you very precise settings.
The barrel ends with a short, immobile ring that turns into a hood mount (a hood is added in the box with the lens). The front element is 54 mm in diameter, slightly convex, immobile, and surrounded by a non-rotated filter thread, 72 mm in diameter.
The lens is weather sealed – splash proof, and dust proof. The front element is also protected against dirt, grease, and moisture retention by hydrophobic coating.
When it comes to optical construction the lens features 14 elements positioned in 11 optical groups. Among them you can find one SLD glass element, and as many as three aspherical elements. Inside there's also a round aperture with 11 blades that can be closed down to a value of f/16.
Buyers get in the box with the lens: two caps, a petal-type hood, and a solid, practical case with a strap.
