I recommend this new field curvature article to anyone seeking maximum image quality (Zeiss user or not), because it shows just how damaging to sharpness a tiny alteration in focus can produce and also how “minimal” field curvature can be a Big Deal.
Side note: I took this image while waiting for better light at dusk. The Nikon D800E is impressive in its usable dynamic range: the quality of the D800E sensor and its 14-bit lossless-compressed NEF files allowed the severe-contrast (almost black foreground) to be brought up. Adobe RAW processing included Highlights = -42, Shadows = +100.
By the way, Mt Dana makes a nice climb. Mt Dana is the peak seen at upper left in the image above.