Zeiss Touit 12mm f/2.8 Distagon: Field Curvature
Published in my review of the Zeiss Touit 12mm f/2.8 Distagon is a study of field curvature behavior.
Field curvature is a very common optical behavior that is well controlled with the 12/2.8 Distagon, but there is worthwhile generalized insight to be had here: the behavior is discussed and analyzed in a manner useful for anyone shooting any lens on any camera.