Archived posting to the Leica Users Group, 1997/07/02

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Subject: Re: Evidence of a Contax/Leica partnership?
From: Martin Tai <cg081@freenet.toronto.on.ca>
Date: Wed, 2 Jul 1997 06:56:48 -0400 (EDT)

On Wed, 2 Jul 1997, Kari Eloranta wrote:

> 
> Martin Tai wrote:
> 
> >On the contrary, the only way to get best optical performance
> >is UNIT FOCUSING, ie,  move the lens as a whole. The internal focusing
> 
> I'm quite sure this is false. For example macros are specialized
> designs for short distances that can be outperformed at infinity.
> And obviously viceversa. Macros don't exist only because some people
> like to get real close, like two inches. Their imageplane flatness etc.
> characteristics etc. are already superior at half a meter which is
> within the distance scale of a SLR normal lens. If your argument would
> be true, a good, fixed, optical formula would work uniformly well at
> all distances (that the lens focuses) which is not true.
> 
> I'm not saying that the Contax design is bad, not at all. In particular
> it allows the user to switch off the AF and do the focusing manually
> with floating elements AND with a tight lens. But to me it seems that
> this type of AF in actual use sacrifices some of the optical potential
> of the lens. 
> 
> Regards,
> 
> Kari Eloranta
> 
> 
   Wrong !
   None of Leica's macro lenses,  Macro-Elmarit 60/2.8, APO-MACRO-ELMARIT
100/2.8 Macro-Elmarit-R 100/4  use  floating element design at all.
   Variable spacing focusing ( internal focusing ) is widely used
in Japanese designs, not favoured by Leica

martin tai