Official: Sigma Art | 20mm F1.4 DG HSM

[9VIII]

Link: http://www.sigma-global.com/en/lenses/cas/product/art/a_20_14/

Price $899 at B&H
Definitely no filter threads.

Diffraction MTF

Geometrical MTF

Vignetting (it's not much different from the 24A and 35A)

Distortion Map