The lens specialist Sigma has released the new f/1.4 DG DN Art attachment for Leica L-mount and Sony E-mount full-frame cameras. With its new arrangement of aspherical, high-refraction and special low dispersion (SLD) elements, it may be well-equipped indeed for portrait shooting. It also has a button that either allows or denies the option of audible clicking in the aperture ring.
https://www.notebookcheck.net/Sigma-announces-its-latest-85mm-Art-series-portrait-lens-for-E-and-L-mount-cameras.484925.0.html