Opticallimits tested the Sigma 56mm f/1.4 DC DN and concluded
The Sigma 56mm f/1.4 DC DN Contemporary is an excellent example for how mirrorless lenses should be. It’s small and well built with a focus on the optical characteristics where it counts the most while compromising on secondary aspects that can be corrected without too many headaches. Namely the sharpness is very good at f/1.4 and downright superb between f/2 and f/8. The laternal CAs are very low. This can’t be said about the original distortion which is on the high side for a prime lens. Vignetting is also very pronounced at f/1.4. However, these two aspects are mostly corrected with image auto-correction either in-camera (with JPGs) or in RAW converters. A strength of the lens is the quality of the bokeh with nicely rendered out-of-focus highlights and a smooth blur in the focus transition zones. Bokeh fringing is present at large aperture but that’s rather normal for such a lens.
The overall build quality is very good. The lens body is made of metal and the big, rubberized focus ring is both smooth as well as very grippy. It also has basic sealing of some kind. On the downside, manual focusing is way too coarse to be useful at shorter focus distances. The AF is about average for a modern mirrorless lens – thus it’s quite fast, noiseless and accurate. You won’t use it for action photography though.
The sum of its qualities combined with the very reasonable price tag make the Sigma 56mm f/1.4 DC DN Contemporary an obvious choice in its class. Therefore – highly recommended!