Get Voigtlander Heliar 10mm f/5.6 Aspherical and Voigtlander Super Wide-Heliar 15mm f/4.5 Aspherical III for Sony at B&H Photo.
My favorite all-around wide angle lens remains the superb Canon 11-24mm f/4L (about $2899), but the 11-24 is heavy and expensive, plus awkward on Sony mirorrless (requires electronic lens adapter as well).
The Voigtlander 10mm f/5.6 offers a 130° field of view, as compared to the 126° field of view for the Canon 11-24/4L at 11mm, and the 121° of the Voigtlander 12mm f/5.6. Going much wider requires a fisheye lens such as the Rokinon FE 12mm f/2.8 fisheye.
My first look at the Voigtlander 10mm f/5.6 is now up:
- Overview of Voigtlander 10mm f/5.6 Asph Aperture Series
- Voigtlander 10mm f/5.6 Asph Aperture Series: Deck Chair (Sony A7R II)
Aperture series includes images up to 28 megapixels along with UltraHD crops, all from f/5.6 - f/11.