Sigma continues to produce exceptionally sharp portrait lenses. Even used wide open at ƒ/1.4, on a full-frame body, the lens produced virtually no corner softness. With a lens at this level of quality, the only reason you want to stop down is to direct how much depth-of-field you want in your image; there is no need to consider the effect on sharpness.
http://www.imaging-resource.com/lenses/sigma/85mm-f1.4-dg-hsm-art/review/
Sony version is in stock
https://www.amazon.com/Sigma-85mm-1-4-Lens-Sony/dp/B07B9W4DNB/
Review
Center sharpness is from very good to top from f/1.8 all the way through to the minimum aperture of f/16. The edges are almost as sharp as the center, with f/2.8 to f/16 producing the sharpest results.
https://www.photographyblog.com/reviews/sigma_85mm_f1_4_dg_hsm_fe_review/sharpness_1/
Sigma 85mm f/1.4 DG HSM ART Lens Deal for $799
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