Re: Evidence of a Contax/Leica partnership?

["Jacques Bilinski" <jbilin@axionet.com>]

> 
> 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?
> 
> Their official line is that you cannot build AF lens to their level
> of mechanical precision. The motors needed to overcome the friction
> from the tight tolerances would need too much power. But to me it
> seems like this should be eventually possible whereas you can never
> overcome the fundamental shortcoming in the Contax solution.
> 
> Any comments from optical experts?
> 
> Kari Eloranta
> 
Contax recomends that the user 'rough focus' first on lenses with floating
elements
(and probably many zooms, and other lenses that are focused by moving only
groups of elements).
 
On conventional autofocus lenses (non-Contax) there is often a small but
noticable amount of play in the lens when it is in its extended position. I
find this a bit disconcerting, but given that most pros use Canons and
Nikons this may not be much of a problem in practice. Given that Leica and
Contax appeal to a market segment of fanatics (like us), this may also have
to do with marketing.

I'm not an optical expert but I imagine that once Leica and Contax have
decided to go with the 'moving film plane' method of autofocus, they will
take this into account as a design parameter when designing new lenses,
likewise other manufactures can  probably design lenses in which the image
degradation caused by the small amount of play in the lenses is minimized.