Autofocus Assist (Electronic Rangefinder) Accuracy

Just published in Making Sharp Images is a new case study of focus assist accuracy with the Nikon D3x using the Zeiss 35mm f/1.4 Distagon, showing the inherently problematic error of the focus assist feature (applies to Nikon and Canon, and is not anything peculiar to Zeiss lenses).

Visibly blurred, even at this small size
Nikon D3x + Zeiss ZF.2 35mm f/1.4 Distagon