DxOMark has tested the Zeiss otus 55mm f/1.4 lens on the Canon EOS-5D Mk III and found it to be one of the sharpest lens around. The following excerpt is from their test results :
"The Zeiss Distagon T* Otus 1,4/55 is the first of a new series of high-grade lenses from the maker optimized for the next generation of high-resolution DSLRs. This fast standard adopts the firm’s retrofocus Distagon type optical construction, a design previously only found on wide-angle models.
It has a complex construction consisting of 12 elements in 10 groups, and features no less than six elements made from anomalous partial dispersion glass and one lens made with an aspherical surface. Although a manual focus design it has a ‘floating elements’ for close range correction and a minimum focus distance of 0.5m.
While the Canon mount (ZE) version lacks an aperture collar like that found on the Nikon (ZF.2) it has CPU contacts for data exchange and electronic aperture control. The result is a slightly longer (144mm vs 141mm) and heavier model (1030g vs 970g) than the Nikon mount version, although it measures the same 83mm at its widest point and retains the 77mm filter thread. The new 1,4/55 Otus is available for pre-order at $3,999 in Nikon and Canon mount only."