Sigma 90mm f2.8 DG DN review
Written by Gordon Laing
The Sigma 90mm f2.8 DG DN is a compact short telephoto prime lens for full-frame mirrorless cameras that costs around $650 or 550 British pounds – and at the time I made this review, available in Sony-e and Leica-L mounts. Sigma loaned me a pre-production sample in the e-mount to try out and you can see how it performs versus the Sony FE 85mm f1.8 in my full video review below! Alternatively if you prefer to read the written highlights, keep scrolling!
The 90 2.8 was launched in September 2021 alongside a new 24mm f2 seen here, both joining Sigma’s steadily growing Contemporary I series. Here’s the new 24 and 90 flanking the earlier 35 f2 in the middle. Add the 65 f2, 45 f2.8 and 24 f3.5 and you now have six compact models to choose from.
The 90 2.8 becomes the longest in the series to date, a perfect focal length for portraits whether you’re shooting stills or video and I’ll show you both along with closeup and landscape comparisons in a moment.
The f2.8 aperture may not be the fastest around, but allows the lens to be pretty compact. In fact at 64x60mm and weighing just 295g, the 90 2.8 is one of the smallest short telephotos with autofocus around. For comparison, here’s Sony’s slightly cheaper FE 85mm f1.8 on the right which at 78x82mm and 371g may still be light but is noticeably chunkier due to its faster aperture. There’s loads of short telephotos around, but since these two cost roughly the same I’m going to show you how they directly compare.
In terms of design and build, the Sigma 90 2.8’s aluminium barrel looks and feels more premium than the Sony – more akin to the Zeiss Loxia 85 2.4 but half the price and with autofocus. Like other Sigma I series models, it’s weather sealed at the mount with a rubber grommet but not throughout the barrel. Sony also claims weather-sealing on the 85 1.8, but I couldn’t see a rubber ring on the mount.
In terms of controls there’s a chunky switch for auto and manual focus, a clicky aperture ring from f2.8 to f22 in one third increments and an A position for body control, and a narrow but smooth and nicely-damped manual focusing ring.
Sony’s FE 85 1.8 sports a customisable focus hold button but no aperture ring, relying on body-based control alone. Meanwhile there’s a slightly wider manual focusing ring than the Sigma.
Like other models in the I series, Sigma supplies not one but two lens caps with the 90 2.8, so as well as the usual spring-loaded plastic cap, there’s an additional metal disc which attaches magnetically, with a satisfying snap and the magnet feels strong enough to keep it in place too. With the hood mounted though, this second cap is a little awkward to fit or remove, so it’s arguably a bit of a novelty, but I like that Sigma’s trying something different here.
At this price point, you might expect a basic plastic hood, but Sigma supplies its I series with aluminium hoods that continue the ribbed style of the lenses for a classy vintage look and feel. I really like the way these lenses look. For comparison here’s the Sony FE 85 1.8 with its plastic lens hood and when fitted it’s a much larger proposition.
Ok, let’s check out the focusing speed and for all my tests in this review I used a Sony A7 III as it was the best body I had access to at this time. You’re looking at Single AFS mode where as usual there’s a minor contrast-based wobble to confirm, but it’s still swift. And for reference here it is again in Continuous AFC mode, where the phase-detect system avoids the wobble.
For comparison, here’s the Sony FE 85 1.8 in AFS mode where you can see the shallower depth of field at f1.8, but also more visible focus breathing as it adjusts between the two bottles. And now in Continuous AFC mode for reference.
Here’s the same test for video with the A7 III filming in 4k and the 90mm at f2.8 and using continuous AF to pull focus between the bottles smoothly and confidently; it’s very quiet too.
And for comparison here’s the Sony FE 85mm at f1.8 where again you’ll notice the potential for a shallower depth of field, but also the more visible focus breathing.
Next for a face detection test with the Sigma 90 2.8, again for movies in continuous AF, with Wide area and human eye detection enabled. The 90mm focal length is perfect for portraits whether stills or video, and while my pre-production lens took a moment to react to changes in distance, it still refocused successfully.
And now here’s the Sony 85 at f1.8 where it too can take a moment to react to changes, and again while the depth of field is shallower, there is that distracting change in magnification as it refocuses.
Sticking with this scene, here’s a still portrait, shot with the Sigma 90 at f2.8. Now while the f2.8 aperture may not be particularly fast, when coupled with the short telephoto length, you can still achieve an attractive blurred background. Now here’s the Sony FE 85mm at f1.8 where you can see how much more blurring you’ll achieve with the faster aperture. Place them side by side with the Sigma on the left and it’s clear the 1.8 lens on the right will unsurprisingly blur the background more from the same distance, so the question for bokeh fans is whether the Sigma delivers enough at f2.8. Let’s also take a closer look at the detail from both lenses, where I’d say the Sigma on the left is a little crisper overall on my eyes, but you may prefer one over the other. And for reference I’ve now swapped out the Sony 1.8 image on the right for one with the lens at the same f2.8 aperture as the Sigma on the left. I’d say the Sigma is still a bit crisper, but the bokeh is a little softer on the Sony. Do you have a preference?
Next for the rendering of bokeh balls from close range, with the Sigma 90 f2.8 near to its closest focusing distance, starting wide-open at f2.8 and gradually closing down in one stop increments. At the maximum aperture the blobs take on cat’s eye shape towards the corner, but are fairly clean with minimal outlining. They become quite circular at f4 before then revealing the shape of the nine blade diaphragm system as it gets smaller.
Let’s briefly return to the Sigma 90 at 2.8 which you’d expect to be less impressive than the Sony at 1.8, but the Sigma can focus much closer, quoting a minimum distance of 50cm. Compare that to the result from the Sony 85 at its closest focusing distance of 80cm and it’s clear any benefit of the faster 1.8 aperture is lost. Here they are side by side. Of course from the same distance, the Sony will win, but if you can get closer, the Sigma has the potential to deliver a shallower depth of field.
Plus of course the closer focusing distance of the Sigma 90 makes it more useful for photographing small subjects. I could reproduce a subject 145mm wide from the closest distance compared to 275mm wide on the Sony. This is a key advantage of the Sigma.
Ok now for performance at a distance with my beach scene angled as usual so that details go right into the far corners. Before taking a close look at the detail I wanted a quick look at geometric distortion starting with the Sigma 90 f2.8 with Distortion Compensation on the Sony A7 III set to OFF, which is the default. With this setting, the Sigma lens exhibits some barrel distortion, so for my in-camera JPEG tests, I changed this setting to Auto where you can see the distortion becomes better-corrected with only a minor crop to the field of view. You can also apply it in post to RAW files.
So here’s the view with the 90mm at f2.8 and taking a closer look in the middle of the frame reveals fine details right out of the gate at f2.8. In my tests closing the aperture didn’t make any visible difference to sharpness or contrast in the middle. Heading out into the far corner and you’ll see the degree of detail remains very high and there’s only very minor darkening due to vignetting too. As I gradually close the aperture, you’ll see there’s little to be gained in sharpness, proving the Sigma 90 is performing very well from the outset. This is a lens you’d be very happy using wide-open.
Ok, now here’s the enlarged view from the middle of the frame with the Sigma 90 on the left and the Sony 85 1.8 on the right, both at their maximum apertures of f2.8 and f1.8 respectively. The Sony’s slightly shorter focal length means the details are a little smaller, but they’re both performing similarly in the middle.
But head out to the corners and the Sony on the right become noticeably softer at the maximum apertures. Of course it’s operating at a faster aperture here, but even as I close the Sony down it doesn’t begin to match the corner sharpness of the Sigma 90 until it’s at around f5.6 to f8. So the Sigma 90 is sharper across the frame at large apertures.
Just before wrapping-up, a focus breathing test for the videographers, starting with the Sigma 90mm f2.8 starting at infinity and gradually focusing manually to the closest distance and back again. As you saw in my autofocus tests earlier, the Sigma 90 is virtually bereft of any focus breathing at all, making it ideal for video use.
In contrast, here’s what happens when you focus the Sony FE 85 1.8 from infinity to the closest distance and back again. Notice how the field of view magnifies, almost like a zoom lens as the Sony focuses closer, and while it starts a little wider than the Sigma 90 as you’d expect, it actually ends up effectively longer when focused close. This is no bad thing for portrait stills, but videographers beware that you will see the change in magnification as you focus this lens.Check prices on the Sigma 90mm f2.8 DG DN at B&H, Adorama, WEX UK or Calumet.de. Alternatively get yourself a copy of my In Camera book or treat me to a coffee! Thanks!