Focus Numerique (google translation here) tested the new Tokina Firin 20mm f/2.0 FE lens. In their eyes this lens is a surprising good performer with only one downside (the position of the aperture ring). Otherwise the optical quality is very high and the lens has no problem to deliver sharp images on a 42 Megapixel sensor. Vignetting and distortion are very low too.
Tokina Firin preorders at BHphoto, Adorama, Amazon UK and at Amazon FR.