Sigma 40mm F1.4 DG HSM | Art (L-Mount)

Reviewers found it sharp across the whole frame from f/1.4, with almost no field curvature, and sharper still by f/2.8. Longitudinal and lateral colour fringing and coma are among the lowest they have measured on an f/1.4 lens, distortion is very low, and wide-open vignetting of about 2.2 stops is milder than on most fast primes. Background blur is smooth with less onion-ring texture than Sigma's 35mm f/1.4 Art.

The universal complaint is size and weight, which make it unbalanced on mirrorless bodies. Flare resistance was rated anything from very good to merely average, with ghosting when the sun sits near the frame. Autofocus was accurate and repeatable but audible, and slower than the Sony 35mm f/1.4 ZA and Zeiss Batis 40mm it was compared with, the focus ring is stiff, and focus breathing is visible.

Owners commenting on a long-form review praise the image quality above all; one says other lenses felt like a step down afterwards, and another calls it the highest-quality lens they have used in decades. The 40mm view at f/1.4 is liked for environmental portraits.

Weight divides them: some got used to it quickly, others find it too heavy for a walk-around standard lens. One notes focus shift that matters on DSLRs but not on mirrorless, and another finds the rendering clean but lacking character.