Sony has officially announced four new conversion lenses – two for full-frame and two for APS-C – that can be screwed onto a select group of lenses. On the full-frame side there are ultra-wide and fisheye adapters for the new FE 28mm F2, which drop the focal range to 21mm and 16mm, respectfully. The adapters for APS-C lenses – the 20mm F2.8 and 16mm F2.8 specifically – and reduce the focal lengths by 0.75X for the ultra-wide adapter and 0.6X for the fisheye. More details.
Articles: Digital Photography Review (dpreview.com)