Tamron 20-40mm F/2.8 Di III VXD Review: Zoom Lens

Tamron keeps broadening its range of optics for Sony E-mount hybrids, and this arrival is one of its most singular: the 20-40mm F/2.8 Di III VXD, a bright wide-angle zoom aimed principally at vlogging. This review is based on the complete published test of the lens, not on hands-on testing of our own.

With its fifteenth optic dedicated to the E-mount, Tamron turns towards the video-diary crowd. Camera makers see vlogging as a growth engine and have multiplied both purpose-built bodies — Nikon Z30, Sony ZV-E10, Panasonic Lumix G100 — and lenses to match, such as Sony's excellent FE PZ 16-35mm F4 G. Tamron already offered an ultra-wide zoom in the 17-28mm F/2.8 Di III RXD; the 20-40 mm brings a no less atypical but somewhat more versatile focal range, and it stands alone on that exact terrain. The closest alternatives are Sigma's 16-28mm F2.8 DG DN Contemporary and the Sony Vario-Tessar T* FE 16-35 mm F4 ZA OSS, alongside the two zooms already mentioned. The lens went on sale in October 2022 towards the top of Tamron's price ladder.

Tamron keeps things sober. The lens measures 8.6 cm long by 7.4 cm in diameter and weighs 365 g — denser in the hand than it appears. Mounted on a small body such as the Sony Alpha 7C, the pairing Tamron itself showed at the announcement, there can be a slight front-heaviness, especially when filming yourself at arm's length without a grip. The dress code follows the brand's recent optics, notably the 28-75mm F/2.8 Di III VXD G2, though the newcomer loses that lens's configurable button. It keeps the USB-C port, which handles firmware updates from a computer or an Android phone through the Tamron Lens Utility app — and allows genuine customisation: the speed of autofocus transitions can be adjusted, and the focus ring can be reassigned to control aperture or exposure instead.

The optical construction counts 12 elements in 12 groups. An internal zoom would have been welcome, but the barrel extends slightly as it travels from 20 to 40 mm. For the more adventurous, the lens is weather-protected — note the gasket around the mount — and should shrug off light rain.

Tamron improves with age: the days when the name meant good value with limited optical performance are long gone. In the published test the lens behaved particularly well, delivering very good sharpness from the widest 20 mm setting and at the full f/2.8 aperture. Maximum sharpness arrives between f/4 and f/5.6, and even f/8 remains an excellent value. Behaviour at mid-zoom (30 mm) is much the same, and at the long end the optic shows its full potential: the widest aperture is of good quality, and from f/4-f/5.6 the sharpness reaches a level rarely attained outside Sony's own high-end glass. The counterpart is fairly poor homogeneity between the corners and the centre of the image, whatever the aperture or focal length.

A very wide zoom means distortion, and this one is no exception: it is quite pronounced at the widest setting, eases at mid-zoom, then becomes markedly stronger at 40 mm. In-camera corrections straighten it out easily on JPEGs and video. Chromatic aberrations earn a very good mark — they are almost invisible. Vignetting is the sore point: very present, particularly noticeable at 20 mm, clearly marked at f/2.8 — and where vignetting ordinarily fades as the diaphragm closes, here it stays visible even at smaller apertures. Internal corrections compensate on JPEGs; raw files will need attention in your editor of choice.

Though it resembles a standard zoom, the 20-40 mm offers less versatility than one. Its wide field of view serves architecture and landscape well, and it is tailor-made for vlogging: at 20 mm it is easy to film yourself without holding the camera far away, while the 30 and 40 mm positions sit close to ideal reportage focal lengths for turning the lens on other subjects. More atypical than a classic 16-35 mm, the range is genuinely useful — though a longer reach to 50 or 60 mm would have been preferable.

Portraits are less its game. Even at 40 mm the subject does not stand out strongly from the background, and the f/2.8 maximum aperture cannot do much more at these focal lengths — though the bokeh bubbles it does produce are very well behaved, round and free of defects. The minimum focusing distance of 17 cm at 20 mm and 29 cm at 40 mm lets you work close to a subject, with due care for the deformations that proximity brings.

Autofocus proved perfectly silent and fully compatible with the advanced systems of Sony's hybrids: the published test ran the zoom on the Sony Alpha 1, Alpha 7R IV and Alpha 7S III without any real focusing trouble. As for the absence of optical stabilisation, it is barely a flaw: every current full-frame Sony hybrid has sensor stabilisation, and so short and bright a zoom carries little risk of shake blur anyway. Only on an unstabilised APS-C body such as the Alpha 6400 does it call for more care — and a 30-60 mm equivalent f/4 remains an easy optic to manage.

Unpretentious at first glance, the 20-40mm F/2.8 Di III VXD in fact delivers excellent image quality, with very effective autofocus motors, in a light and compact build. Anyone hoping to make it more than a first-class video tool will find the focal range short on versatility; in its intended role, it is entirely convincing.