If you shoot on an APS-C mirrorless camera and want one lens that stays on the body most of the time, there's a good chance the Sigma 18-50mm F2.8 DC DN Contemporary is already on your shortlist. It's small, sharp and keeps a bright F2.8 aperture through the whole zoom range. Now Tamron has a direct rival: the new Tamron 16-50mm f/2.8 A, which starts 2mm wider.

We took both lenses out around Sydney on a Sony a6600 for street, low-light portrait, architecture and video shooting, then compared the files side by side. The short version: optically, we struggled to tell them apart. Your choice comes down to whether you need the wider 16mm view, plus a few practical differences in video behaviour, close focusing and price.

• Choose the Tamron 16-50mm F2.8 if you shoot architecture, interiors, landscapes or vlogs, where the extra width at 16mm changes what you can fit in the frame. It also breathed less when focusing in our video test, and it adds weather sealing through the barrel and app-based customisation.

• Choose the Sigma 18-50mm F2.8 if you mainly shoot street, travel, everyday and portrait work and rarely feel limited at 18mm. It matched the Tamron for image quality in our side-by-side shots, it focuses closer at the wide end, it's slightly lighter, and it's the less expensive option with a $134 difference.

Either way, you won't be disappointed. Both are excellent small standard zooms.

Sigma specifications from Sigma's official specification page. The Sigma's weight varies slightly by mount (285 g for Fujifilm X, 290 g for Sony E and L-Mount, 300 g for Canon RF). Full-frame equivalents use a 1.5x crop factor; on Canon's 1.6x APS-C bodies, the equivalents are a little longer.

On paper, 16mm versus 18mm sounds trivial. In practice, the wide end is where small numbers make a big difference, because each millimetre changes the angle of view much more than it does at the long end. On a typical 1.5x APS-C camera, 16mm frames roughly like a 24mm lens on full frame, while 18mm frames roughly like 27mm.

We saw this clearly from Observatory Hill. Shooting the Harbour Bridge at each lens's widest setting, the Tamron fitted noticeably more of the city into the frame.

It mattered even more when we photographed Crown Sydney up close. When a building fills most of the frame, that extra width gives you room to correct converging vertical lines in editing and crop without cutting off the top of the building. With the Sigma at 18mm, we simply had less room to work with.

For vloggers, the difference is bigger again. Digital stabilisation, whether in camera or in your editing software, works by cropping into the frame. Start at 18mm and add stabilisation, and you can quickly lose the background or end up too tight on yourself at arm's length. Starting at 16mm gives you that margin back.

If you rarely shoot wider than 20mm or so, though, those 2mm won't change much for you. On the street, we found we weren't shooting at the very widest setting much anyway.

Street and travel

These lenses are designed to be small and easy to carry, so we started where they're most at home: walking the city at golden hour, waiting for people to pass through patches of light. Both lenses made it easy to flick between focal lengths and recompose quickly, and in the hand neither felt like it held us back.

Comparing the street shots side by side, there was very little in it. Both were sharp where it counted, contrast was punchy straight out of camera, and the colour was close enough that we struggled to pick them apart. The real giveaway was framing: at the wide end, the Tamron fits in a little more.

The conditions weren't identical. We shot the Tamron first and the Sigma afterwards, as the wind picked up and the light faded, so treat this as a real-world comparison rather than a lab test.

Low light and background blur

Both lenses keep F2.8 across the whole zoom range. That matters because the aperture doesn't shrink as you zoom in, so you keep the same light-gathering and the same ability to blur the background at 50mm as at the wide end.

We photographed our cameraman, Mitch, at 50mm and F2.8 at night, with city lights behind him. Both lenses produced smooth, creamy backgrounds and rendered the lights nicely, and both shots were well exposed in that low light. For such small lenses, the portrait results genuinely impressed us.

Up close on the computer, it was a really close call. Both lenses use seven aperture blades. Tamron says theirs stay rounded for two stops down from wide open, so if you stop down to F4 for a little more depth of field, out-of-focus highlights should keep a round shape rather than turning into polygons. Wide open, you'd be hard pressed to pick one from the other.

Watch in the video: The low-light portrait comparison shows the background blur and light rendering more clearly than stills on a web page.

Sharpness

To check sharpness, we took the same shot with both lenses across a range of apertures and compared them on a laptop. At F2.8, the centre was crisp on both, with detail right across the subject. Towards the corners, both softened a little wide open, which is normal for compact zooms like these, and there was very little between them.Stop down to just F4 and both sharpen up nicely from edge to edge.

Honestly, we couldn't pick a winner.

The Sigma stops down further, to F22 compared with the Tamron's F16. Unless you're deliberately chasing a sunstar or need a very slow shutter speed without a filter, you're unlikely to use either extreme, so we wouldn't base the decision on it.

Could you tell them apart?

In the video, we put pairs of images on screen and asked viewers to guess which came from which lens. We found it genuinely difficult ourselves. After going through all the images side by side, our conclusion is that, optically, these two lenses are very close to identical. The meaningful difference is the 16mm wide end.

Watch in the video: Try the blind comparison yourself before reading the answer.

Both lenses focused quickly and tracked well with the Sony a6600's subject tracking. Their motors are different: the Sigma uses a stepping motor, while the Tamron uses Tamron's VXD linear motor, which Tamron says is designed for fast, quiet focusing on moving subjects such as children and animals. In our use, we didn't see a practical speed difference, and neither motor was audible in our footage, so both are suitable for run-and-gun video.

Where the Tamron did pull ahead was focus breathing. That's the slight change in framing you see when a lens shifts focus between near and far subjects, which can look distracting in video. As focus moved, the Tamron's frame barely changed, while the Sigma's breathed noticeably. If you film interviews, product shots or anything with deliberate focus pulls, that's a real advantage. For stills, it doesn't matter.

Watch in the video: Focus breathing is much easier to see in motion. Watch the edges of the frame as focus shifts.

The Sigma focuses noticeably closer at the wide end. Sigma rates its maximum magnification at 1:2.8 at 18mm, compared with 1:4.5 at 16mm for the Tamron. In practice, that means small subjects such as food, flowers or product details can fill more of the frame with the Sigma.

At the 50mm end, the difference is much smaller, with Sigma listing 1:5 maximum magnification and Tamron 1:4.8.

If you shoot a lot of close-up detail for social media, product content or travel, the Sigma’s stronger wide-end magnification is one of the clearest reasons to favour it beyond price.

In the hand, these lenses feel very similar. The Sigma is made in Japan at Sigma’s Aizu factory and the Tamron is made in Vietnam, but we don’t think that should sway your decision. We couldn’t find a meaningful difference in build quality.

We did notice a couple of small differences in handling. The Tamron’s zoom ring felt smoother to us, while the Sigma’s had a bit more resistance towards the long end. The Sigma has a nice matte finish that we think looks a touch more professional.

On our scales, the Sigma weighed 283g and the Tamron 303g. The Tamron is also slightly taller and wider. On the camera, neither difference was very noticeable. An extra 20g for 2mm more at the wide end is a good trade.

Weather resistance is where the Tamron goes further. Tamron says it has moisture-resistant seals through the barrel and a fluorine coating on the front element, which helps water and fingerprints wipe straight off. Both lenses have some sealing at the mount. If you travel or shoot outdoors in changeable weather, the Tamron’s extra protection is worth having, though neither replaces sensible care in heavy rain.

The Tamron has a USB-C port on the side of the barrel. Connect it to TAMRON Lens Utility Mobile on your phone, or the desktop version on PC/Mac, and you can customise how the lens behaves, including:

• the direction of the manual focus ring
• the focus ring’s response, whether linear or non-linear, and its rotation angle
• manual focus control directly from your phone
• firmware updates (PC/Mac version only)

To connect your phone, you’ll need the TAMRON-Link Bluetooth adapter (sold separately, and required for iPhone) or, on Android, Tamron’s USB-C connection cable. For firmware updates on PC/Mac, any USB-C cable will do. Lens Utility works fully on Sony E and Nikon Z versions. On Canon RF it’s limited to firmware updates, and it isn’t available on Fujifilm X.

Controlling focus from your phone is the standout. We were able to rack focus in and out without touching the camera at all, which is useful on a tripod or gimbal, for product video, or anywhere touching the lens would shake the shot. It’s a niche feature for many stills shooters, but a genuinely practical one for video.

Watch in the video: See focus being pulled from the phone with no hands on the camera. 

Is the Tamron worth the extra money?

Based on our side-by-side comparison, you’re not paying more for better image quality. You’re paying for:

• 16mm at the wide end, which matters most for architecture, interiors, landscapes and vlogging
• Less focus breathing, which matters for video
• More comprehensive weather sealing, with leak-resistant seals throughout the barrel, a water-proofed USB-C port and a fluorine-coated front element
• App customisation, including focus control from your phone

The Sigma counters with closer focusing at the wide end, slightly lower weight and a lower price. At $615 versus $749 for the Tamron, it’s $134 cheaper.

One flag: the Tamron quote you pulled confirms the seals and the USB-C port, but it doesn’t mention the fluorine coating. It’s worth double-checking that before it goes live, since the build section mentions it too.

Our recommendation: if you need the extra width, the Tamron is worth it. If you mostly shoot street, travel, portraits and everyday photos and don’t feel restricted at 18mm, save the money and buy the Sigma. You’ll get the same image quality.