Intro

The Sigma 28-70mm f2.8 DG DN is a general-purpose zoom lens for full-frame mirrorless cameras, and at the time of writing, available in Sony e or Leica L mounts. Announced in February 2021 at a price of $899 or 759 pounds, the Sigma 28-70 provides a more affordable option for those who want a walkaround zoom with an f2.8 aperture but can’t stretch to pricier not to mention heavier models that zoom wider to 24mm.

Sigma loaned me a final production sample in the Sony e-mount and in the video below I’ll show you how it performs for landscapes, portraits, close-ups, and general use. If you prefer to read a written version, keep scrolling!

For starters, here’s the optical range in practice, starting at 28mm for standard wide views, before zooming into 70mm for short telephoto coverage. By starting at 28 rather than 24mm, Sigma’s been able to reduce the cost and weight.

The 28-70mm f2.8 DG DN measures 72x102mm and weighs 470g. Compare that to the 24-70mm f2.8 DG DN Art, launched just over a year earlier, which is noticeably larger at 88x123mm and getting on for double the weight at 835g. The new 28-70mm also uses smaller 67mm filter threads versus 82mm on the 24-70 Art, although is only weather-sealed at the mount versus the whole Art lens. Price-wise the 24-70 2.8 DG DN Art costs $1099 or 1049 pounds, making it around 200 bucks or 300 pounds more expensive than the 28-70 Contemporary version. Both are significantly cheaper than Sony’s own FE 24-70mm f2.8 G Master which sells for around 2000 dollars or pounds and weighs 886g.

Starting a little less wide to save weight and money isn’t a new idea. Tamron’s first native e-mount lens was the 28-75mm 2.8 Di III RXD launched around three years earlier and currently costing $879 or 699 pounds. Measuring 73x118mm and weighing 540g, it’s a little longer and a tad heavier than the Sigma 28-70, but it’s roughly in the same ballpark in size, weight and price. I’ve fully reviewed the Tamron 28-75, as well as the Sigma and Sony 24-70’s at cameralabs.com and will update my review of the new Sigma with direct comparisons as soon as I can.

Both the Sigma and Tamron f2.8 zooms are designed not only as lighter and more affordable alternatives to 24-70mm f2.8 models, but also as step-ups from budget kit zooms like Sony’s own FE 28-70mm f3.5-5.6 which costs roughly half their price but suffers from a dimmer and variable aperture that’s two whole stops slower at the long-end. Okay let’s see what the new Sigma’s all about.

From the side the Sigma 28-70 is pretty straightforward. A short angular throw on the zoom ring gets you from the wide to the long-end with the barrel extending by 23mm. There’s only one switch on the barrel which toggles between manual or autofocus, while at the end is a smooth motor-assisted focusing ring. There’s no optical stabilisation, so anti-shake has to be provided by your body.

Sigma supplies a thick plastic petal lens hood that can be fitted backwards over the barrel for transportation, while an equally robust spring-loaded cap clips onto the 67mm filter thread.

At the lens mount you’ll find a rubber grommet providing some dust and moisture resistance, but unlike the 24-70 2.8 Art version, this doesn’t extend to the rest of the lens, so use with caution in bad weather. This is the same approach as Sigma’s recent DG DN Contemporary prime lenses, not to mention Tamron’s 28-75.

Now for focusing on the Sony A1 using a central area and single AFS mode at 70mm f2.8 and you can see there’s a minor contrast-based wobble at each focus-pull to confirm, but the process is still fairly swift and quiet too. Switching the A1 to Continuous AF mode though forces the body to use phase-detect AF alone which here is refocusing noticeably faster than before, and in my tests didn’t reduce accuracy. So it can be worth experimenting to find the best mode.

Here’s the lens again at 70mm f2.8 with continuous autofocus and wide area working fine with the A1’s eye detection tracking me effortlessly around the frame. Notice the almost complete absence of focus breathing here which I’ll talk about more in a moment.

70mm f2.8 isn’t particularly demanding for sports or wildlife, but I tried it out on the A1 with Brighton’s seagulls and in these sequences you can see the lens successfully tracking the eyes of the birds as they swooped past at close range. Keep an eye on your chips and donuts!

In my final focus test I wanted to check for breathing where the magnification can vary as you focus. Here’s the lens at 24mm, focusing between infinity and the closest distance and back again, and while there’s a minor change in magnification it’s fairly well-behaved.

Set the lens to 70mm though and as you focus from the furthest to the closest and back again, the lens is impressively bereft of breathing with the magnification essentially remaining unchanged throughout – great news for videographers.

Now for a short range portrait test, here with the Sigma 28-70 at 70mm f2.8 where as you’ve seen before it’s possible to achieve a nice subject separation without completely destroying the background or context. The rendering of blurred areas here also looks nice and smooth

If you prefer more in focus, here’s how the lens looks closed one stop to f4 and even when viewing the full image I’d say the rendering in the background has become noticeably busier.

Let’s take a closer look with the f2.8 shot on the left and the f4 version on the right where it’s clear the f4 version looks crisper on my eyes. I think my lens and body combination are fractionally mis-focusing at f2.8 when using eye detection, and repeating the tests didn’t improve the result. In contrast at f4 the details around my eyes become much crisper, although I personally now find the rendering in the background busier and less attractive. To be fair the f2.8 version looks fine when viewed in isolation and don’t forget I’m also showing you results using an unforgivingly high resolution sensor, but in my portrait tests the lens lacked the absolute subject crispness of higher-end lenses when shot wide-open.

Rendering of blurred areas is always something I like to test and compare so here’s the 28-70 2.8 at 70mm, shot from the closest focusing distance at this focal length, quoted as 38cm.

In terms of the quality of rendering, there’s minimal outlining, but clear evidence of onion-ring patterns within the blobs. It’s not ideal but to be fair a similar amount of onion-ringing is also visible on the Tamron 28-75 and even on the more expensive Sigma and Sony 24-70 2.8 models. If you prefer smoother bokeh blobs in this kind of situation, you’ll be better served by a prime lens than any of these zooms.

For one more bokeh comparison, here’s the Sigma 28-70 at 28mm f2.8, as close as it can focus at that focal length, quoted as 19cm. There’s still some texture within the blobs, but it’s still a fairly attractive result and I enjoyed the potential for shallow depth-of-field effects when shooting at close range. Note the lens does become softer in the corners the closer you focus.

As for actual macro reproduction, here’s a ruler shot from as close as the lens would focus at 70mm, and at f2.8 notice how the details towards the edges have become quite soft. Closing the aperture gradually improves the edge performance but even at f8 it’s still soft at the extremes. So stop down if you’re archiving flat subjects, but if the main subject’s only in the middle you can get away with larger aperture.

Zoomed to 28mm you can get surprisingly close to the subject and still enjoy a sharp centre, but the quality greatly deteriorates as you move towards the edges, especially at large apertures. Closing the aperture gradually improves the sharpness away from the centre, but there’s still a lot of distortion here so it’s best used for subjects that are kept in the middle.

Now for the quality at landscape distances, starting with the lens at 28mm f2.8, and like all my shots in this review, it was taken with the Sony A1 using the default lens corrections, so Shading and Chromatic aberration compensation set to Auto and Distortion set to Off.

Taking a close look in the middle reveals plenty of fine details even with the aperture wide-open, and closing the aperture makes little difference to the quality.

As you move into the corners, the sharpness remains fairly consistent, with softening only really appearing in the very extremes. The biggest issue though is vignetting, or darkening in the corners, even with shading compensation turned on. Closing the aperture one stop to f4 greatly alleviates vignetting, while closing another stop or two also boosts the sharpness in the far corners.

Next here’s the view at 50mm, roughly mid-way through the range, and with the aperture wide-open to f2.8.

Taking a close look in the middle again reveals nice fine details even coupled with the high res A1 body, and closing the aperture isn’t necessary to boost the detail.

Moving into the corners shows the lens is roughly maintaining a good degree of detail, although with the aperture wide-open there’s a little softness in the extreme corner plus some darkening due to vignetting. As before, closing the aperture gradually improves the quality, brightening the corners and boosting the detail. If you’re a pixel-peeper with a high-res body, it’s definitely worth shooting detailed views at f5.6 or f8 rather than wide-open.

And finally here’s the view at the long-end of the range, at 70mm and again open to f2.8.

Looking closer in the middle again shows decent detail which again looks pretty good out of the gate at f2.8.

Moving into the corner again shows some softness and darkening at the extremes, which as before gradually improves as you close the aperture. Again things are looking good across the frame at f5.6 and f8.