Some discussion is warranted here. This lens's center of the frame performance is outstanding, even wide open at f/1.8. Primarily at issue are the soft corners falling below expectations, with all four corners performing similarly. At the 14mm full frame angle of view, a very close focus distance is required to fit even a large chart in the frame, and my first thought was perhaps the close-focusing image quality was the issue. However, some quick outdoor testing also shows relatively soft peripheral performance even at very long distances, though as usual, natural details appear better than the sharp, high-contrast test chart. So, I next need to make a decision on how to proceed.
If this retail-purchased lens is performing properly, it might be worth carrying the additional weight of the Sigma Art Lens. Here is that comparison.