Tamron 20-40mm F2.8 Di III VXD verdict
Summary
The Tamron 20-40mm F2.8 Di III VXD is not for everyone. At first glance, it’s an odd sort of crossover lens somewhere between a wide-angle zoom and a kit lens, but with a 2x zoom range that sounds distinctly limiting. But Tamron is trying to create a new kind of lens that crosses conventional categories, and I think it’s rather good. That 2x zoom range offers more framing and perspective variation than you might expect, the constant f/2.8 maximum aperture is excellent at this price and the handling is smooth, light and sweet. I’ve realized that around 80% of my shots are taken within this zoom range, and it’s become my go-to Sony kit lens.
Pros
+ Surprisingly useful ‘walkaround’ zoom range
+ Constant f/2.8 maximum aperture
+ Excellent optical performance
+ Fast and silent VXD AF motor
+ Compact and lightweight
Cons
– No aperture ring
– No VC Vibration Compensation
– Limited (for some) 2x zoom range
Introduction and context
The Tamron 20-40mm F2.8 Di III VXD has a very unusual focal range. It doesn’t fall into any of the normal categories for zoom lenses. It’s not wide enough to be a typical ultra-wide zoom like a 16-35mm, and it’s not long enough to replace a typical standard zoom like a 24-70mm. It falls somewhere between these two categories and doesn’t seem to do either job as effectively.
But that’s only one way of looking at it. There’s another. Instead of buying lenses that fit into known categories, just because that’s the convention and everybody else does it, why not look at the focal lengths that you, personally, use most often? That’s why I bought this Tamron, because I realized that a large proportion of my casual walkaround landscape/travel/architectural photography is in this focal range.
Sometimes I might want a wider focal length, occasionally I might want a longer one, but as veteran single-lens shooters will know, you have to work with the lens you’ve got and you just find somewhere different to stand or compose the shot differently.
The Tamron 20-40mm F2.8 Di III VXD is one of just a few extra-wide-standard zooms. Other examples include the Sony FE 20-70mm f/4, the Lumix 20-60mm f/3.5-5.6 kit lens and the OM System M.Zuiko 8-25mm f/4.
Tamron says this lens is especially suited to video, and it has a point. First, it uses Tamron’s VXD AF actuators which, as far as I can tell, are as fast and silent as other maker’s top-end linear motors. Second, it’s an ideal focal range for vloggers filming themselves at arm’s length. The minimum 24mm of a regular standard zoom is barely wide enough, but the 20mm focal length of this lens gives you a much wider frame. Third, it hardly changes at all in length as you zoom and the focus is internal. If you put this on a gimbal, I don’t think you’ll have to rebalance it every time you change the zoom setting. Most decent gimbals will have enough power in the motors to overcome the small weight shifts of this lens while zooming.
Tamron 20-40mm F2.8 Di III VXD specifications
| Focal range | 20-40 mm (30-60mm on APS-C) |
| Angle of View | 94°30′-56°49′ |
| Maximum aperture | F2.8 (constant) |
| Minimum aperture | F22 |
| Lens construction | 12 elements in 11 groups |
| Diaphragm Blades | 9 |
| Minimum focus distance | 0.17m (20mm), 0.29m (40mm) |
| Maximum Magnification Ratio | 1:3.8 (20mm), 1:5.1 (40 mm) |
| Filter Size | 67 mm |
| Dimensions (W x L) | 74.4mm x 86.5mm |
| Weight | 365 g (Sony E-Mount) |
Tamron 20-40mm F2.8 Di III VXD features
So what are the other key features of this lens? Apart from the unusual focal range, it has a constant f/2.8 maximum aperture. This might not sound much of a technical achievement given its limited 2x zoom range, but it’s faster than any of its current extra-wide-standard zooms rivals, the best of which offer a constant f/4, not f/2.8.
This is a formidable achievement, not just in general, but particularly at this price. The Tamron 20-40mm F2.8 Di III VXD is considerably cheaper than any roughly equivalent own-brand lens (not that there are many, to be fair).
The optical construction uses some pretty sophisticated glass, consisting of 12 elements in 11 groups, which include four LD (low dispersion) elements, two GM (glass molded) aspherical elements and one hybrid aspherical element.
The zoom range might be relatively short, but this lens makes up for it, perhaps, in its focus range, with an impressive shortest focus distance of 0.17m at the 20mm focal length, though this does increase to 0.29m at 40mm. You get the highest magnification at the shortest focal length, which isn’t alway ideal.
It’s also worth mentioning Tamron’s lens utility app. This isn’t just for updating firmware. It can also be used to customize the lens controls and, if you connect your phone to the lens via USB, you can use the app to set up custom focus pulls between selected distances. This is ideal for more cinematic shooting setups where the camera is on a tripod and you get to direct the action. Who knew a Tamron lens could do that?
Tamron 20-40mm F2.8 Di III VXD design and handling
Anyone who owns a full frame mirrorless camera knows that constant-aperture zooms aren’t small. I use my Tamron 20-40mm on my Sony A7 II, which kind of exacerbates any imbalance since these are pretty small camera bodies. Compared to most constant f/2.8 lenses, though, the Tamron 20-40mm is quite compact, light and manageable. According to Tamron, it’s also moisture and splash-resistant..
It’s certainly an extremely pleasant lens to handle and use. The zoom ring is light, smooth and very sweet. It also has a short travel, along with the lens barrel itself. It’s shortest at the 40mm setting, but zooming out to 20mm extends the lens barrel only a short distance – about 1cm.
There is no aperture ring on this lens. That is a bit disappointing, but then you tend to have to pay a lot more money for this kind of sophistication.
There’s no focus distance scale, either – lens makers hardly seem to bother these days – but the zoom ring does have focal length markings for 20mm, 24mm, 28mm, 35mm and 40mm. This isn’t just an aid to composition, but a reminder that this lens can replace a whole set of individual f/2.8 primes, if you choose to look at it that way.
None of this is any good, of course, if the lens doesn’t perform well, so that’s the next key question.
Tamron 20-40mm F2.8 Di III VXD performance
I was and still am surprised at just how good this lens is. I’m used to wide-angle zooms being a bit poor at the edges, even more expensive ‘pro’ lenses. I had to get rid of my Zeiss 16-35mm f/4 because I couldn’t trust the edge definition. I also returned my new Fujifilm XF10-24mm F4 for the same reason – not helped by Fujifilm’s switch to a 40MP sensor. Higher resolutions always show up a lens’s weaknesses, so optical performance does matter.
There are no such problems here. I’m sure a lab test chart would reveal a decline in resolution at the frame edges, but I don’t think it’s significant in real-world images, and I’m one of the world’s worst pixel peepers. At 20mm the edge-to-edge definition is stellar and it’s almost as good at 40mm. I think I can see just a slight drop in performance at the 40mm end of the zoom range, but I do mean slight, and sometimes I’m not sure I can see it at all.
If this was a Sony G Master lens I wouldn’t be surprised. This is what you’re paying for, after all. But it’s not. The Tamron 20-40mm is a fraction of the price. And yet I would happily use the Tamron even on the higher-resolution Sony A7R II that I owned, or even a 61MP Sony A7R V.
The Tamron 20-40mm does rely on digital lens corrections. This is now standard practice for mirrorless lenses across all manufacturers. If you shoot JPEGs this will happen in-camera; if you shoot RAW then Lightroom, Capture One, DxO PhotoLab and no doubt others will have a correction profile.
I’m equally impressed by the autofocus. It’s fast, it’s silent and I can see it being just as good for video as it is for stills photography.
Tamron 20-40mm F2.8 Di III VXD verdict
At first sight, the Tamron 20-40mm F2.8 Di III VXD might seem a rather odd sort of in-between lens with a relatively short zoom range and a rather plain design. If you habitually shoot at wider or longer focal lengths, then this one won’t meet all your needs and you might be better off with a regular pairing of a 16-35mm zoom, say, and a 24-70mm.
But that’s not how I see it. The 20-40mm focal range is where I take 80% of my photographs unless I’m on some specific photo assignment – in which case I would choose different gear. But for casual walkaround photography, the Tamron 20-40mm F2.8 Di III VXD suits me perfectly. Its image quality is surprisingly good, its build and handling are surprisingly slick, it’s surprisingly compact and light and even the price is a bit of a surprise at around $699 / £749.