Light and compact. Inexpensive. Excellent resolution. 1:2 magnification. Dust, splash, and fluorine protection. 

The Tamron 20mm f2.8 Di III OSD M1:2 is an ultra-wide prime lens for Sony’s E-mount mirrorless cameras and corrected for full-frame use. It’s part of a three lens series from Tamron all of which have the distinguishing feature of a maximum magnification of 1:2. 

Jan 01, 2020 ·  Tamron 20mm f/2.8 Di III OSD M1:2 Handling and Features. Clearly, weighing in at a very modest 220g, there is an extensive use of plastics in the lens construction. 

The Tamron 20mm F/2.8 Di III OSD M1:2 is a fairly fast, ultra-wide-angle prime lens for Sony's extensive range of full-frame and APS-C sensor mirrorless cameras. It features a maximum aperture of f/2.8, an Optimized Silent Drive focus motor for quiet AF operation, and a moisture-proof construction. 

Jan 28, 2020 ·  If you’ve already got a 28-70mm or even a 24-70mm zoom lens for your full-frame Sony E-mount camera, and want something that gives a greater viewing angle without bulking up your kit or weighing you down, this Tamron 20mm f/2.8 Di III OSD M 1:2 should prove the perfect fit. 

Apr 03, 2020 ·  The OSD motor is quieter than the Sony, but it is still fairly audible--similar to the 18-135 SAM. This lens has a high amount of barrel distortion more than the 24 mm. The Tamron supplied Lens Compensation corrects it fine in-camera or in Capture One. Unfortunately Capture One mistakes this lens for the Sony E 20mm F2.8 pancake. 