The source is a new pillowcase for the guestroom, set near a window (natural light). It was shot using the macro 35mm end of the old Nikon 35-70mm f/2.8 lens.

Clearly the upper left is soft...perhaps the lens, perhaps the pillow not being a flat surface. I suspect the latter, since the lower-left and upper-right are in focus to the edge, and these were the flat, long surface of the pillow, while the upper-left and to a lesser degree the lower-right were the edges that fell away slightly.