The Sigma 28-70 mm F2.8 DG DN is ideal for compact cameras such as the Sony A7C or the Sigma FP. 

Sigma already has a bright standard zoom: the Sigma 24-70 mm F2.8 DG DN Art. Why then a standard zoom with the same brightness but a slightly more limited range? That has everything to do with dimensions and weight. The new 28-70mm F2.8 is significantly lighter at 470 grams than the 24-70mm F2.8, which weighs 835 grams. That’s a serious difference for photographers watching the weight of their equipment. The 28-70mm F2.8 is also shorter than the 24-70mm F2.8, and it has a smaller filter size at 67mm.

What do you give up to achieve such low weight and such compact dimensions? According to Sigma, the quality of the 28-70 mm F2.8 DG DN is comparable to that of the Sigma 24-70 mm F2.8 DG DN Art. The big difference is in the 4mm that you lose in the wide-angle mode. That may not seem like much, but in terms of field of view, that’s the difference between 85 degrees at 24mm or 75 degrees at 28mm. As a user, you will have to determine how heavily that weighs. The great thing is that you really have a choice with Sigma.

A lens with which the 28-70 mm F2.8 DG DN must of course also be compared is the Tamron 28-75 mm F2.8 Di III RXD. It has roughly the same specifications and advantages as the Sigma. However, the Sigma is even shorter and about an ounce lighter than the Tamron. The Sigma also has an AF-MF switch that the Tamron does not have. On the other hand, the Tamron has 5mm extra range on the telephoto side and is completely weatherproof. The Sigma only has a gasket on the mount.

BUILD

The housing of the Sigma 28-70mm F2.8 DG DN is made of high-quality plastic. This naturally contributes to the low weight. The lens is made with small tolerances to keep out moisture and dirt, but is – unlike the Sigma 24-70 mm F2.8 DG DN Art – not completely weatherproof. The 28-70 mm F2.8 does have a gasket on the mount, and the front lens has a special coating that makes it easier to keep clean.

With the 28-70 mm F2.8, the focus ring is at the front and the zoom ring is behind it. That’s like the majority of all zooms. It may be a reason to prefer the Sigma over the Tamron, where the rings are exactly the other way around. The optical design consists of 16 elements in 12 groups. Four elements are made of special types of glass, and three elements are aspherical. The aperture has nine rounded blades for optimal bokeh. 

FOCUSING

The Sigma 28-70 mm F2.8 DG DN has a quiet and fast stepper motor for the autofocus and an AF-MF switch for quickly switching from autofocus to manual focus. The shortest setting distance is 19 cm in the wide-angle position and 38 cm in the telephoto position. The maximum magnification scale that you achieve with this is 1:3.3 at 28mm and 1:4.6 at 70mm. That’s fairly macro already.

IMAGE QUALITY

We don’t have the lens in our test lab yet. However, the MTF curves look good and are hardly inferior to those of the Sigma 24-70 mm F2.8 DG DN Art. As soon as we have a review copy, we will of course publish a full test.

ConclusiON: REVIEW Sigma 28-70mm F2.8 DG DN op Sony A7R III