Field review: Sigma 28-70mm F2.8 DG DN

Introduction

 

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Overall score

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The Sigma 28-70mm F2.8 DG DN Contemporary lens is a very compact, lightweight standard zoom lens for full-frame and APS-C mirrorless cameras. It boasts a constant F2.8 maximum aperture across its zoom range and is available for both the Sony E-mount, as well as for Leica, Sigma and Panasonic cameras from the L-mount Alliance.

It’s aimed at photographers and videographers who want a bright walkaround zoom and the bokeh possibilities that a wide aperture brings but who don’t want the size, weight and cost typical of many F2.8 zooms. Travel and landscape photographers in particular will find its modest size and weight appealing, and it also offers potential as a portrait lens or for video capture.

Available now, the Sigma 28-70mm F2.8 DG DN Contemporary carries a list price of $899.

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Handling | Autofocus and focus breathing | Image quality | Conclusion | Samples

All images edited in Adobe Camera Raw 13 with adjustments limited to white balance, exposure, highlights, shadows, white and black levels. Sharpening and noise reduction at ACR defaults.

Key specifications:

• Mount: E-mount (Sony) or L-mount (Panasonic, Leica, Sigma)
• Focal length: 28-70mm (42-105mm on APS-C bodies or with APS-C crop)
• Aperture range: F2.8 – F22
• Stabilization: None
• Filter thread: 67mm
• Close focus: 0.19m (7.5″) wide / 0.38m (15.0″) tele
• Maximum magnification: 0.30x (wide) / 0.22x (tele)
• Diaphragm blades: 9
• Hood: Included
• Weight: 470g (1.04 lb)
• Optical construction: 16 elements in 12 groups (2 FLD, 2 SLD, 3 aspherical)

ISO 100 | 1/320 sec | F8 | 36mm | Panasonic S1R Photo by Barney Britton

There are several alternatives to the Sigma 28-70mm F2.8, although only one of these is available for both the E-mount and L-mount: The Sigma 24-70mm F2.8 DG DN Art. It’s priced $200 higher, is 21.4mm (0.8in) longer and fully 75% heavier.

For the added cost and heft, the Sigma 24-70mm Art offers even better image quality and includes an 11-bladed aperture. It also provides a little extra wide-angle coverage and full weather sealing. If you can stretch your budget a little further, we find it’s a worthwhile choice.

ISO 100 | 1/500 sec | F5.6 | 42mm | Panasonic S1R Photo by Barney Britton

Sony E-mount shooters also have access to the more affordable Tamron 28–75mm F/2.8 Di III RXD. It’s just 16.3mm (0.6in) longer, weighs 80g (2.8oz) more, and gives you a fractionally more powerful 75mm telephoto than the Sigma 28-70mm. It also offers full weather-sealing versus the mount-only sealing of the Sigma 28-70mm F2.8.

Yet despite coming in lighter and smaller than the Sigma, it’s $100 less expensive. But if portability is your primary concern and you don’t need all-weather shooting capability, then the Sigma’s length and weight savings are certainly enough to be noticeable.

The deep-pocketed and less size/weight-conscious may also want to consider the Sony FE 24-70 mm F2.8 GM ($2099.99) for E-mount or the Panasonic Lumix S PRO 24-70mm F2.8 ($2199.99) for L-mount. Both are not only significantly pricier but also just a little larger and heavier again even than the Sigma 24-70mm Art.

Compared to…

Handling

As you might expect, the featherweight Sigma 28-70mm F2.8’s body is predominantly constructed from polycarbonate, although it does still have a metal mount and build quality is good. And while it isn’t fully weather-sealed like its nearest rivals, the mount still includes a seal that should help protect your camera body from the elements, if not the lens itself.

And since it is so lightweight, balance is very good. Regardless of the mount variant you choose, it shouldn’t feel front-heavy on any body you might want to pair it with.

With no built-in image stabilization, there are only three controls in total: A pair of very nice, well-dampened zoom and manual focus rings and a focus mode selector switch on the left side of the barrel.

Up front, you’ll find 67mm filter threads. That’s the same size as used by its Tamron rival, while the Sigma 24-70mm F2.8 opts instead for a larger 82mm filter thread.

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Autofocus and focus breathing

Autofocus comes courtesy of a stepper motor that drives just a single lightweight focusing element, and the result is swift and silent AF. It takes just one second or less to fully rack the autofocus from the 19cm (7.5in) minimum focus distance to infinity. The linear motors in the Sony 24-70mm F2.8 GM or Canon’s RF 24-70mm F2.8L may be a tad faster, but for most use cases, the Sigma’s autofocus is more than fast enough.

Despite its fairly close focusing distance, this isn’t a true macro lens. The maximum magnification of 0.30x (1:3.3) occurs at wide-angle, and if you zoom to the 70mm position, you’ll need to move back to 38cm (15in) from your subject, resulting in a weaker but still respectable 0.22x (1:4.6) magnification at telephoto.

ISO 100 | 1/1000 sec | F2.8 | 61mm | Panasonic S1R Photo by Barney Britton

In terms of video autofocus, the Sigma 28-70mm DG DN has the potential to be a really great option. Not only does it offer silent autofocus drive and very nicely-damped manual focus, but it also has well controlled focus breathing. There’s only a bit at the 28mm wide-angle end and very little at all by the time you zoom in to 70mm.

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Image quality

Life is all about compromises. With a bright, continuous aperture and minimal size and weight being the key elements of its design, it’s not surprising at all that the Sigma 28-70mm F2.8 DG DN’s image quality can’t quite compete with larger, more expensive alternatives like Sigma’s own 24-70mm F2.8 DG DN Art.

That said, the 28-70mm F2.8 Contemporary still offers solid image quality. This is especially true if you’re willing to stop down a bit, don’t shoot with an extremely high-res body or don’t need perfection in the corners. Let’s take a closer look.

ISO 100 | 1/80 sec | F4.5 | 49mm | Panasonic S1R Photo by Barney Britton

Sharpness

Shooting wide-open at F2.8 (which you’ll quite likely want to spend much of your time doing if you’ve bought this lens for its bright maximum aperture), sharpness is very acceptable in the center of the frame at 28mm and remains pretty good even once you zoom in to the 70mm telephoto.

Stopping down to F5.6, we see a slight improvement in sharpness at wide-angle and a bigger improvement at telephoto, since the lens is softer wide open at 70mm than it is at 28mm. You’ll appreciate this improvement in sharpness more if you’re shooting with a high-resolution camera. We tested with both the 42-megapixel Sony A7R III and 47-megapixel Panasonic S1R; with a 24-megapixel body, that difference would be much less noticeable.

ISO 100 | 1/500 sec | F2.8 | 58mm | Sony A7R III Photo by Chris Niccolls

Sharpness drops off a little at the corners on the wide end at F2.8, but stopping down to F5.6 gives a relatively flat field of focus and improved corner sharpness. That said, focusing in the corner yields higher corner sharpness than focusing in the center and stopping down, indicating a curved field of focus. Focusing in the corner and stopping down yields even better corner sharpness, as expected. The not-so-flat field of focus, at least in part, contributes to the peripheral softness when focusing centrally.

This might be an issue if you like to shoot landscapes (or brick walls) wide open but, practically speaking, stopping down the lens will yield decent edge sharpness. Meanwhile, if you need optimal sharpness off-axis, simply use an off-center AF point (rather than using the ‘focus and recompose’ method).

Results at 70mm follow a similar pattern, but with softer results overall, particularly at close focus distances. Wide open, portraits can often look a little dreamy.

ISO 100 | 1/1250 sec | F5 | 61mm | Panasonic S1R Photo by Barney Britton

For most practical purposes, however, the Sigma 28-70mm is easily sharp enough. For portrait shooting, just make sure you use an AF point over your subject for focus to overcome any issues with field curvature, as you should with any lens and modern autofocus system. And for wide-angle landscape shooting, stopping down to F5.6 will help, and by the time you reach F8 or F11, you’ll be really pleased with the results.

Vignetting and distortion

When it comes to distortion, we need to discuss the Leica L-mount and Sony E-mount versions of the lens separately. That’s because if you’re an L-mount shooter, distortion is corrected automatically in both JPEG and Raw files, but if you’re shooting Raw on the E mount variant on a Sony body and using Adobe software, there’s (currently) no correction applied for distortion.

Distortion isn’t an issue for the L-mount version thanks to automatic correction, but Sony E-mount variants show some barrel distortion at wide-angle and prominent pincushion at telephoto.

Shooting on a Sony A7R III body, our samples show some barrel distortion noticeable at wide-angle, which changes to become quite prominent pincushion by telephoto. By contrast, our samples shot on a Panasonic Lumix DC-S1R show practically no distortion, thanks to automatic correction. Raw shooters of any mount who use Capture One have more options here, as it can use the embedded distortion correction metadata to correct the image.

Vignetting is not a concern for the Sigma 28-70mm F2.8. It’s only really noticeable at telephoto, and even there is minor and easily corrected.

Bokeh

There’s both good news and bad news on the bokeh front. The Sigma 28-70mm F2.8 DG DN’s bokeh has a really pleasing, smooth look to it, with only minimal onion ring effect and smoothly-rounded, step-free edges even when stopped down to F4.

For the most part, bokeh is very pleasing, with only very slight onion ring and a nice, polygon-free shape even when stopped down to F4. ISO 100 | 1/200 sec | F4 | 70mm | Sony A7R III Photo by Chris Niccolls

On the other hand, it’s quite prone to cat’s eye effect when shooting wide-open, giving the bokeh more of a football (or for non-Americans, rugby ball) shape the closer it gets to the corners. And that problem is not limited just to those corners but extends quite a long way towards the center of the frame.

While out-of-focus highlights start taking on a football-like shape fairly quickly away as you leave the central region of the frame, the good news is the effect is fairly modest until you reach the very edges and corners. Here, the effect is not so much cats eye as it is truncation of the optical cone due to mechanical obstruction (see the odd shapes in the image below).

Cat’s eye effect is quite noticeable when shooting wide-open and can appear quite a long way towards the center of the image frame. ISO 3200 | 1/80 sec | F2.8 | 70mm | Sony A7R III Photo by Chris Niccolls

Stopping down helps significantly, though it doesn’t entirely solve the problem at the extremes of the image. To be fair, this is an issue with most 24-70mm F2.8 lenses.

Overall, though, we really enjoyed the Sigma’s thin depth of field and ability to yield soft backgrounds that help draw your viewers’ focus to the primary subject, especially for portrait shots. And the falloff from out-of-focus to in-focus and back again is also rather nice.

Flare, ghosting and sunstars

The Sigma 28-70mm F2.8 turns in a decent performance when it comes to ghosting. Even when shooting into the sun or with it in the corner of the frame, there was only a little ghosting noticeable in the far opposite corner. However, flare can be an issue, and you may see a noticeable loss of contrast when shooting with a bright light source in the frame.

ISO 100 | 1/1600 sec | F2.8 | 70mm | Sony A7R III Photo by Chris Niccolls

Sunstars are relatively pleasing, with 18 rays thanks to the nine aperture blades. They’re not as tight as they could be – each ray splits and diverges into two rays – and as expected stars on the wide end look better than those on the telephoto end where they can appear a bit ‘messy’.

ISO 100 | 1/40 sec | F16 | 28mm | Sony A7R III Photo by Chris Niccolls

Lateral and longitudinal chromatic aberration (fringing)

We didn’t see any major issues with lateral chromatic aberration for this lens. There’s a truly minute amount of it, perhaps 2-3 pixels wide on a 42MP image (that’s a half a millimeter on a 40″ x 60″ print) that clears up easily if you enable CA corrections in-camera or in your Raw converter.

There’s just a little bit of longitudinal chromatic aberration, visible as color fringing, around high contrast edges of slightly out-of-focus regions, but as you can see in the sample below, it’s not really anything to concern yourself over. It disappears immediately upon stopping down.

A little bit of longitudinal chromatic aberration can be seen as magenta and cyan color fringing around high contrast edges in the image above. It’s subtle enough to be a non-issue for the most part, and goes away as you stop down the lens. ISO 100 | 1/400 sec | F@2.8 | 70mm | Panasonic S1R Photo by Barney Britton

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Conclusion

At the end of the day, it’s important to bear in mind the target customer when evaluating the Sigma 28-70mm F2.8 DG DN Contemporary. Can more money get you an upgrade in the image quality department? Absolutely, as always. But it’ll also come at the additional cost of a significantly larger, heavier lens. If you’ve got to pack it for air travel or carry it with you while out hiking or roaming around town on foot, that added size and weight will be a disadvantage.

ISO 100 | 1/100 sec | F4 | 45mm | Panasonic S1R Photo by Barney Britton

Sure, it has some caveats in the image quality department. Most notably, corner sharpness isn’t stellar at telephoto while wide-open; close-up telephoto shots wide open can have a soft dreamy look, and it’s also quite prone to cat’s eye bokeh effect. But honestly, depending on your subjects, those may not be major concerns for you. And image quality is otherwise solid, with very good sharpness across much of the focal range, pleasing bokeh, and good resistance to aberrations and ghosting.

ISO 100 | 1/13 sec | F4.5 | 49mm | Sony A7R III Photo by Chris Niccolls

The Sigma 28-70mm F2.8 is also well-suited to video capture, with swift and silent autofocus and nicely-damped controls, as well as minimal focus breathing. Its only other significant shortcoming is the lack of full weather-sealing, something offered by all of its nearest rivals. If you expect to shoot rain or shine, that may be a deal-breaker, but if not, then it represents an opportunity to save some money while getting better portability.

If you prioritize outright image quality and durability over size, weight and cost, we’d recommend the fully weather-sealed Sigma 24-70mm F2.8 DG DN Art. And for E-mount shooters who are more size, weight and cost-conscious but who need to shoot regardless of the elements, the Tamron 28–75mm F/2.8 Di III RXD also offers a compelling alternative if you can live with its more distracting bokeh.

On the telephoto end the maximum magnification ratio is 0.22x. Close-up subjects shot at 70mm can appear soft and dreamy. ISO 250 | 1/200 sec | F2.8 | 70mm | Panasonic S1R Photo by Barney Britton

But if what you need most of all is portability and you understand the compromises necessary to achieve it, the Sigma 28-70mm F2.8 DG DN is hands-down the smallest and lightest of the bunch and still offers solid image quality.

It doesn’t hurt that it’s also among the most affordable F2.8 full-frame standard zoom options for the E- or L-mounts. For the size, weight and cost-conscious, it’s definitely worthy of consideration.

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Sample galleries

Please do not reproduce any of these images without prior permission (see our copyright page).

Samples shot with the Panasonic S1R

Samples shot with the Sony A7R III

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Scoring

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