RE: [Leica] Mechanicals and optical quality

[Alexey Merz <alexey@webcom.com>]

"Kotsinadelis, Peter (Peter)" <peterk@lucent.com>:
>Alexey,
>Nice try but the only thing you are saying is that older lenses may have
>better mechanics.

Yes, that is what I am saying. Compare the construction of many older
scientific instruments with many of the newer ones. The average Zeiss
research microscope of thirty years ago blows the average 'scope of 
today out of the water in strictly mechanical terms. 

Part of the reason for this is that they often incorporated adjustment
settings designed to compensate for wear. Modern designs often don't.

Rigidity, lack of backlash in docusing, etc. are very often better on
thirty year old scopes that have been in continuous use than on 
brand new units. Optically, modern 'scopes are better. No argument.

>Yes this is important but composite materials of today
>can be made to a far more accurate degree than the old brass lenses.

I do not think that this is necessarily the case. The major advantages
that composites offer are lightness/strength ratio, low coeff. of
thermal expansion (especially for ceramics, where Kyocera is a [the]
world leader), and in some cases, cheaper manufacturing. But most
composites do not do better as high-precision bearing surfaces, as
in focusing helicals and lens mounts. That high-end lenses from ALL
manufacturers use steel for bayonet mounts (including Contax/Kyocera/
Zeiss) while cheap lenses use thermoplastics, attests to this.

Composites/plastics are used in autofocus lenses in preference to 
metals for two reasons. They are cheaper to manufacture, particularly
when injection molding replaces complex machining or casting, and they
are lighter. This is critically important when one is trying to minimize
the size, mass, and battery consumption of an autofocus system.

>Add to that electronic control for 99% aperture and shutter accuracy
>and in the end you are saying that modern lenses and cameras may 
>actaully be better.  I shutter to think that......Pun intended.

I have NO doubt that modern lenses are better, *including* those from 
Zeiss and Leica. Note that few composites are used in Zeiss manual
focus lenses.

My point was that lens ALIGNMENT is a defining parameter for optical
performance, and that the mechanics therefore DIRECTLY influence 
long-term maintenance of optical performance.

I have no doubt that Contax G and Leica M lenses both give 
wonderful performance outof the box... BUT I would bet that
Leica M lenses will retain near-optimal optical characteristics
for longer than their Contax G counterparts, given similar levels
of (ab)use.

Note that this evaluation does *not* apply to Contax/Leica SLR lenses.
..........................................................................
Alexey Merz | URL: http://www.webcom.com/alexey | email: alexey@webcom.com