There have been no direct rivals of the Sigma A 28-45 mm f/1.8 DG DN on the market so far; that's why in our chart we are comparing it with other well-put-together constructions of that type, so the Sigma A 24-35 mm f/2.0 DG HSM, mentioned by us in the introduction, and the Canon RF 28-70 mm f/2L USM.
Compared to the reflex camera 24-35 mm model the weight of the new Sigma didn't change significantly but its length increased in a distinct way. Now you see clearly the price of increasing the maximum focal length. With slowing down the aperture to f/2.0 the RF system Canon is over 50% heavier than the tested Sigma. It's also worth noticing that both Sigma lenses are closed constructions – the change of the focal length doesn't increase their dimensions. In the case of the Canon the situation is different, and it's an additional fee to pay.
In the photo below the Sigma A 28-45 mm f/1.8 DG DN is positioned between the reflex camera Sigma A 35 mm f/1.4 DG HSM and the Voigtlander Apo-Lanthar 2/50.
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The tested lens starts with a metal mount that surrounds the contacts and a rear element, 27 mm in diameter. That element is situated about 1 cm deep inside the barrel. Above it you see a rounded 32x26 mm frame. The inner tube is properly blackened and matted so from this side everything looks very well.
The proper body of the lens starts with a smooth, black, metal ring that increases its diameter very quickly. On that ring there is a white dot, making the alignment with a camera easier, an inscription “MADE IN JAPAN”, the 024 number meaning the model year, and the focusing mechanism working range:„0.3M/0.98FEET–∞”.
Further on you see an aperture ring. It is as wide as 18 mm and most of its surface is covered by rubber ribbing; apart from the ribs there are aperture markings from f/16 to f/1.8 and also an A value (auto). The ring moves every 1/3 EV step but it can also be declicked, an option that will make filmmakers very happy. Overall the ring is a joy to use – no reservations here.
Further on you see an immobile part covered by plastics with the logo of the company, the name and parameters of the lens, its serial number, some fine ribs and a whole array of switches. The first of them – FOCUS AF/MF- is used to choose the focusing mechanism working mode. The other one – CLICK- controls modes of the aperture ring. On the other side you find an aperture ring lock that can block it either at A position or at any other point in a range from f/1.8 to f/16.
The next part is a focus ring, 28 mm wide, most of its surface covered by rubber ribbing. Under the ring you find focal markings at 28, 35, 40, and 45 mm. The ring moves smoothly and is well damped across its whole range.
Further on you see an immobile part of the lens partially covered by fine ribs. On it you see an A letter meaning the lens was classified as an Art line device, and two round FOCUS LOCK buttons that, additionally, are programmable.
A manual focus ring is the next part of the proper barrel, almost completely covered by rubber ribbing. It is a focus-by-wire mechanism and its focus throw depends on the speed of your turning. When you move the ring faster it amounts to approximately 180 degrees, when you turn it slower you can reach even nearly 450 degrees. Both these are values allow you very precise settings.
The Sigma A 28-45 mm f/1.8 ends with an edge where you can attach a hood mount and inside there is a non-rotating filter thread, 82 mm in diameter. The front element doesn't move, is quite convex, 57 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.Other optical elements are covered by anti-reflection Nano Porous Coating and Super Multi-Layer Coating.
When it comes to optical construction there are overall 18 elements set in 15 optical groups. You deal here with as many as five low dispersion SLD elements and three aspherical ones. Inside you also find 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: both caps, a hood, and a hard case.
