Emme. This old Petzval lens has a very peculiar area of focus. It took a few tests even before I knew what to test. The depth of field is shaped not like a square block as in a Macro lens, nor is it a convex space like a regular prime lens, it’s more like a red blood cell in shape. (Lens looking into the deepest part of the bowl shape of a cell) Focus on any edge and the middle is out. Focus on the middle, like the above, and everything outside of the focus spot is out. Nice to have a 4x5 so you can avoid center punching the focus spot. Now I understand why early large format photos were matted with a curved top. They were avoiding the fall off of the top of the circle of illumination because they were trying to shift the sharp to the top third of the image.