Japanese company Tamron has announced the 17-70mm f/2.8 Di III-A VC RXD for Canon RF and Nikon Z mounts, bringing an APS-C zoom that was first released for Sony E-mount in late 2020 to two additional mirrorless ecosystems. The lens covers a 4.1x zoom ratio at a constant f/2.8 aperture — a combination that, at the time of its original release, was the first of its kind among APS-C zoom lenses.

On Nikon Z APS-C cameras, which apply a 1.5x crop factor, the lens delivers a 25.5–105mm equivalent range. On Canon RF-S bodies, with a 1.6x crop factor, the equivalent range extends from 27.2 to 112mm. The two new mount variants are otherwise nearly identical to the E-mount version, with one exception: the Nikon Z version omits the physical AF/MF and VC on/off switches present on the barrel of the Sony and Canon versions, delegating those functions to the camera’s menu system — a consistent approach Tamron applies across its Z-mount lineup.

The optical construction uses 16 elements in 12 groups, with a nine-blade circular aperture diaphragm and a 67mm front filter thread. Vibration Compensation is built into the lens. Minimum focusing distance is 19 centimeters at 17mm and 39 centimeters at 70mm, with maximum magnification of 1:4.8 and 1:5.2 respectively. The RF-mount version weighs 530 grams and measures approximately 120mm in length; the Z-mount version is 540 grams and marginally longer. Both feature moisture-resistant construction and a fluorine coating on the front element.

The context for both releases differs by mount. On the Nikon Z side, the APS-C ecosystem gained a Nikkor Z DX 16-50mm f/2.8 VR last year, but the Tamron lens extends the reach to 70mm at the same aperture. On the Canon RF side, existing RF-S zooms top out at f/4.5–6.3 with variable apertures, making the Tamron one of the few fast constant-aperture zoom options available to Canon APS-C users — a situation Canon has enabled by opening the RF mount to third-party autofocus lenses, though only for APS-C format.