Field curvature – or why the ZM C-Sonnar is soft in the corners
I was playing iwth the Zeiss ZM C-Sonnar the otehr day and noticed some significant curvature of field ide open and close up. No wonder the mtf is so poor* in the corners! This was taken at f1.5 (focus on the middle apple) and about 0.9m. Just look at the branch coming towards the camera that remains in focus right to the edge of frame!
* the mtf curve is a function of the lens’ design. The lens is one of my favourites, but this amused me.