Flying Start

Tamron’s first lens in the Sony FE mirrorless mount is appropriately a standard zoom, but with the twin attractions of an f2.8 constant aperture and an affordable price tag.

Things are hotting up in the Sony FE mount world and not just because more third-party lens makers are joining the club, but also because Sony itself is fast-tracking a program of new lenses, including more high-end ‘G Master’ models. And it’s going to get hotter now that Sony finally has some competition in the full-35mm mirrorless space, although it has a very substantial head start on Canon and Nikon which you can be sure it’s determined to maintain (starting with the promise of 12 more FE lenses within the next year or so). In terms of lens choice, it’s going to remain the best served full-35mm mirrorless system for a good while yet.

Manual focusing collar is a fly-by-wire control, but maintains a well-weighted feel.

Tamron has sensibly kicked off its FE mount program with a 28-75mm standard zoom which immediately provides an interesting alternative to Sony’s own 28-70mm and 24-70mm models. Tamron’s new zoom has a constant aperture of f2.8 so Sony’s 28-70mm – at f3.5-5.6 – is significantly slower, but also a lot cheaper too. The 24-70mm also has a constant aperture of f2.8, but it’s obviously not quite as long at the telephoto end.

However, it’s also a ‘G Master’ model so it’s significantly pricier (actually well over twice the price). At around $1300 then, the Tamron 28-75mm looks like a good balance of extra performance at a more affordable price.

On the outside, the styling is quite similar to Sony’s 28-70mm, but not surprisingly, it’s a little bigger overall and the positions of the zooming and focusing collars are reversed.

There are no other controls, not even an AF/MF switch, and the styling is essentially basic matte black, save for a champagne gold-coloured ring around the mount.

The Tamron zoom’s barrel is weather sealed and there’s a fluorine coating on the exposed surface of the front element to help better repel moisture and grease. This also makes for easier cleaning, although many users will no doubt fit a protective filter anyway, especially as the screwthread fitting is 67 millimetres so these won’t be too expensive.

The front element’s exposed surface has a fluorine coating to help better repel moisture and grease, and enable easier cleaning.

Working Glass
On the inside, the optical construction uses 15 elements in 12 groups with a total of five being special types. These comprise three with aspherical surfaces – one glass moulded and two hybrid types – one with extra-low dispersion (‘XLD’) characteristics and one with low-dispersion (‘LD’) characteristics.

The latter pair of special elements principally deal with chromatic aberrations while the trio of aspherical elements is designed to correct for distortion. Glass moulding makes the creation of complex element surfaces much easier than the traditional technique of cutting and polishing, while the hybrid design also makes it more economical. Hybrid aspherical elements are created from a spherical core with an optical resin outer layer used to form the necessary surface shaping. This optical design plus the use of GRP barrel tubes helps keep the total weight down to just 550 grams. Tamron’s ‘BBAR’ (Broad-Band Anti-Reflection) multi-coating is employed to help minimise flare and ghosting.

The 28-75mm zoom employs a new type of autofocusing motor which Tamron calls ‘RXD’ and this is short for ‘Rapid eXtra-silent stepping Drive. Stepping motors are starting to be used more frequently in camera lenses primarily because they allow for smoother and quicker operation which has benefits for subject tracking when shooting video. Additionally, they are nearly totally silent. Tamron has opted for a focusing group design which gives a variable minimum focusing distance, ranging from 19 centimetres at 28mm to 39 centimetres at 75mm. However, the telephoto end still delivers the maximum reproduction ratio which is 1:4 or one-quarter lifesize. This is actually represents pretty handy close-up capabilities for a standard zoom and the diaphragm employs nine blades which gives a more rounded aperture and hence smoother out-of-focus effects.

The external construction is weather sealed, which includes a gasket

Handling And Performance
The Tamron 28-75mm feels comfortably balanced on any Sony A series mirrorless body, and the zooming range is fully traversed in a short twist of just under 90 degrees. The focusing collar is an electronic ‘fly-by-wire’ control, but still feels reasonably well-weighted and responsive.

Importantly, Tamron’s FE lens supports Sony’s ‘DMF’ (Direct Manual Focus) function which provides a full-time manual override of the autofocusing. It also supports Sony’s in-camera corrections for vignetting, chromatic aberrations and distortion plus the ‘Eye AF’ and ‘Fast Hybrid AF’ operations on the later A series mirrorless bodies. With no AF/MF switch on the lens, obviously focus mode switching is done via the camera.

While the Tamron doesn’t have optical image stabilisation, correction for camera shake is available in the Sony bodies with sensor-based image stabilisation which includes the second-generation A7 models and the current A7 III, A7R III and A9. Sony’s five-axis IBIS is very effective and will give up to 5.5 stops of correction on the A7R III.

There was a convenient overlap in the test periods of the Tamron 28-75mm zoom and Sony’s A7 III so we were able to evaluate the lens on the very latest A series body. The Sony’s excellent autofocusing continued to work fast and flawlessly with the Tamron zoom, including when using the ‘Eye AF’ to track faces moving around the frame. Overall, the subject tracking – which is a highlight of the Mark III A7 cameras – remained very reliable even with small or fast-moving subjects. The ‘RXD’ focusing motor’s operation proved to be virtually inaudible
in practice and was undetectable on movie soundtracks recorded with the A7 III’s built-in stereo microphones.

Obviously having a constant maximum aperture of f2.8 is one of the key attractions of this lens, so how does it perform wide open?

Overall, the uniformity of sharpness and brightness from centre-to-corner is very good across the zooming range, but there is some slight fall-off in both at between 28mm and 35mm. In terms of sharpness, it’s not significant though, because this lens really is very sharp… surprisingly so, in fact. At 50mm, the centre-to-corner sharpness is exceptional for a zoom. Vignetting is a little more pronounced at 28mm and f2.8, but significantly reduced by stopping down to f4.0 and completely eliminated at f5.6. Alternatively, it can be handled by the in-camera processing which seemed effective enough with the A7 III and there didn’t seem to be a noticeable increase in noise in the corners as a result.

Distortion is very well controlled so it’s visually non-existent at the 28mm end, but very slight pin-cushion bending is evident at the 75mm focal length in situations where a straight line is located immediately adjacent to the frame edge. Otherwise, though, it won’t be noticeable at all. Chromatic aberrations are also very well managed optically so overall sharpness isn’t compromised even before in-camera correction does its thing.

ABOVE & BELOW: Lens tested on Sony A7 III. Test files exhibit excellent overall sharpness, including centre-to-corner uniformity which, while good at 28mm and f2.8, is truly exceptional at between 35mm and 50mm. Some vignetting is evident when shooting wide-open at 28mm, but it’s effectively eliminated by stopping down. Both colour and contrast are very good and the Tamron zoom’s optics also deliver effective correction for distortion and chromatic aberrations.

The Verdict
We know that Tamron has been kicking a lot of goals with new lenses recently, but somehow we didn’t expect the FE mount 28-75mm zoom to be as good as it is. Perhaps because it’s an unprepossessing lens on the outside and the basic spec is fairly standard fare in these days of exotic zooms, but this lens truly delivers in terms of performance and, consequently, it proves to be a very competent all-rounder for everyday shooting, in fact, Tamron has balanced the focal range and maximum aperture with the key objective of optimising performance – particularly sharpness – while maintaining manageable dimensions and an affordable price tag. It’s actually no mean feat in optical terms. There are no frills, but you don’t miss them when a lens performs this well in all the key areas of sharpness, brightness and distortion. Comfortable handling and useful close-up capabilities add a bit more spice to the mix. Tamron may be a bit late getting to the Sony FE mount party, but the 28-75mm f2.8 zoom ensures that it’s going to make a lasting first impression.

Tamron 28-75mm f2.8 Di III RXD Zoom (Model A036)
Price: $1299

Format: Full-35mm digital sensors. The focal range is equivalent to 42-112.5mm on the ‘APS-C’ format (with a 1.5x focal length magnification factor).
Angle-of-View: 75.23 to 32.11 degrees (diagonal on 35mm format).
Construction: 15 elements/12 groups.
Minimum Focus: 19 cm to 39 cm (28-75mm).
Maximum Reproduction Ratio: 1:2.9 (at 28mm).
Aperture Range: f2.8 – f22.
Overall Length: 117.8 mm.
Maximum Diameter: 73.0 mm.
Filter Diameter: 67 mm.
Weight: 550 grams.
Lens Mount(s): Sony FE.
Features: Weather-proofed barrel and mount, fluorine coating on the front element’s external surface, two hybrid aspherical elements, one glass moulded aspherical element, one XLD (extra-low dispersion) glass element, one LD (low dispersion) glass element, ‘BBAR’ (Broad-Band Anti-Reflection) multi-coating, ‘RXD’ autofocusing drive, internal focusing group, nine-blade diaphragm, continuous manual focusing override. Bayonet mount lens hood supplied.