The launch of the Sigma A 28 mm f/1.4 DG HSM was an interesting even, concerning a very demanding segment with fierce competition. First of all, the Sigma has serious rivals among its own Art line, like very well made A 1.4/24 and 1.4/35 models.
solid and stylish casing,, sensational image quality in frame centre,, very good image quality on the edge of the APS-C/DX sensor,, good image quality on the edge of full frame,, lack of problems with longitudinal chromatic aberration,, slight lateral chromatic aberration,, imperceptible distortion,...
very high vignetting at the maximum relative aperture on full frame,, performance against bright light leaves a bit to be desired.