Just published in my Zeiss Guide is an aperture series in 1/2 stops from f/2 through f/16, for the Zeiss 25mm f/2.8 Distagon. This series is a companion to the same series for the 25mm f/2 Distagon, and should make interesting reading for anyone considering either of the Zeiss 25mm lenses.
Since there is no ZE version (for Canon) of the 25mm f/2.8 Distagon, this series is in 1/2 click-stops manually on the lens (using a lens adapter on the Canon 5D Mark II). In fact, lens adapters are the way I shot the Zeiss ZF lenses for Nikon for years on Canon bodies.
This image was shot wide open at f/2.8. It is common practice for me to shoot my Zeiss lenses wide open for the vignetting effect useful in isolating the subject. Stopping down for maximum detail is hardly the only way to shoot landscapes, even banal at times. See Landscape Photography at Wide Apertures in DAP.