Re: Evidence of a Contax/Leica partnership?

[Paul Schliesser <paulsc@eos.net>]

>If I understand it correctly the Contax way of doing autofocus is
>suboptimal. Meaning that one achieves better optical performance
>if in focusing the relative positions of the elements in the lens
>are changed instead of just changing the distance of the whole lens
>from the film plane. Leica is all for the ultimate optical performance,
>in R anyway. Why would they go for the Contax solution?

This is only true if the lens uses "floating elements." Mainly zooms and 
over-200mm lenses, and maybe some lenses with aspherical surfaces, use 
floating elements, although there are exceptions. Some AF lenses focus 
with floating elements for purely practical reasons, especially if they 
are large or heavy; it's faster and easier to move a few lens elements 
internally with a little motor than to move the whole lens with a big 
motor.

Most manual focus prime lenses focus by moving the whole lens closer or 
farther away from the film plane, so there is no difference between what 
the Contax AX does and the way the lens focuses normally.

- - Paul