Just published in my Guide to Zeiss ZF / ZE Lenses is a comparison of the Zeiss ZE 35mm f/1.4 Distagon and Zeiss 35/2 Distagon and Canon 35/1.4L on a scene which shows field curvature behavior.
I strongly recommend reading this new comparison, even if you don’t intend to use the Zeiss 35/1.4 Distagon, as it applies in general to lenses of any brand (and lens comparisons). See also Making Sharp Images.
New York professional photographer James K writes:
Your article on field curvature is quite illuminating. Great job. Unique reporting- truly original material.