A recent leak shows that Tamron is expected to announce a new fast ultra-wide lens later this month. Rumored to be called the 11-20mm F/2.8 Di III-A RXD, it would mark a first for the Sony E-mount APS-C system: a constant aperture f/2.8 ultra-wide zoom lens. Currently Sony's only own-brand offering that comes close is the E 10-18mm F4 OSS, which though 1mm wider, is a whole f/stop slower throughout its aperture range.
Not only would the 11-20mm F/2.8 Di III-A RXD offer a large constant aperture, it looks set to do so while also being very compact and lightweight. Early details suggest the lens would be just 86.2mm long with a 73mm maximum diameter, resulting in a 67mm front filter thread.
The Tamron 11-20mm F/2.8 Di III-A RXD is a welcome shot in the arm (not a COVID joke) for Sony APS-C camera fans. Tamron has already announced its full frame Tamron 150-500mm F/5-6.7 Di III VC VXD for full frame Sony cameras, and that too will fit the Sony APS-C models. The 11-20mm F/2.8 Di III-A RXD, however, is an APS-C only lens that offers an ultra-wide zoom range and constant f/2.8 aperture – that's the spec of a professional lens.
The key feature of the new Tamron 11-20mm F2.8 zoom is that it's the world's first constant f/2.8 ultra-wide-angle zoom lens for Sony E-mount APS-C mirrorless cameras. Even Sony doesn't make one; its best effort here is the Sony E 10-18mm F4 OSS, which is a whole f-stop slower – though the Sony lens does have optical image stabilization, which the new Tamron lens does not. If you want image stabilization you'll need to pair this lens with an A6500 or A6600 body, both of which include sensor-shift image stabilization, though IS is generally considered less important with wide-angle lenses anyway.
Constant f/2.8 lenses are usually very big, but the Tamron 11-20mm F2.8 measures a manageable 86.2mm in length and weighs just 335g.
At the 11mm focal length it has a minimum object distance of 15cm, which gives a maximum magnification ratio of 1:4. This is ideal for exaggerated perspective effects with small foreground objects.
The optical configuration consists of 12 elements in 10 groups, and includes two "precisely located" GM (Glass Moulded Aspherical) lens elements for edge to edge sharpness.
The Tamron 11-20mm F2.8 Di III-A RXD uses Tamron's RXD autofocus system (Rapid eXtra-silent stepping Drive) with a precise rotational actuator which doesn't need a reduction gear, and a sensor that precisely detects the position of the lens for fast, accurate AF for both stills and video.
Tamron is pitching the 11-20mm F/2.8 Di III-A RXD as an ideal companion for its existing 17-70mm F/2.8 Di III-AVC RXD lens, also for APS-C E-mount cameras. With this pairing, you get an 11-70mm combined focal range and an f/2.8 constant aperture throughout, yet the total combined weight of both lenses would still be a reasonable 860g – and both share the same 67mm filter size.
Tamron 11-20mm F2.8 Di III-A RXD specifications
Full frame: No
Image stabilization: No
Focal Length: 11-20mm (16.5-30mm equivalent)
Compatible Mounts: Sony E-mount (APS-C)
Maximum Aperture: F2.8
Minimum Aperture: F16
Aperture Blades: 7 (circular diaphragm)
Angle of View (diagonal): 105° 20'-71° 35'
Optical Construction: 12 elements in 10 groups
Minimum Object Distance: 0.15m /5.9 in (WIDE), 0.24m /9.4 in (TELE)
Maximum Magnification Ratio: 1:4 (WIDE) / 1:7.6 (TELE)
Filter Size: 67mm
Maximum Diameter: 73mm
Tamron 11-20mm F2.8 Di III-A RXD price and availability
The Tamron 11-20mm F2.8 Di III-A RXD will go on sale one June 24 2021, at an expected retail price of $829/£819.99.