Here is a lost interview from the Createasphere Expo 2010. I did this for another website called The Photoletariat. There is some good info here, so I thought it is worth posting.
I was lucky enough to ask Richard Schleuning from Carl Zeiss a few questions. I must admit that every time I speak to him I learn something new. The way he is able to break down a lens is simply amazing. Here he explains how an auto focus lens will never be as precise as a manual focus lens. An auto focus lens is constantly compensating while a manual focus lens is locked off at any given focal length. It’s a simple case of mechanics. We shot this interview with a Zeiss 35mm f1.4 prototype. Badass lens.