[Klaus]

Klaus, may I ask, what distance you mean by close focus, practically? Around min focus distance, or longer?

 

I didn't do any formal testing from where the quality decreases substantially.

While the images aren't meant for that the softness is quite apparent on the bokeh fringing images.

 

The Zeiss has a floating system similar to macro lenses so it's not surprising that it manages to keep the quality on a very high level.