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Re: [OM] Noctilux versus Zuiko [was: [OM] While we werefighting...[origi

Subject: Re: [OM] Noctilux versus Zuiko [was: [OM] While we werefighting...[originally mailed Thurs. AM]]
From: "Mark Hammons" <astaire@xxxxxxx>
Date: Sun, 5 Aug 2001 22:32:55 -0500
> >
> >I didn't realize the original Nocticlux tested so poorly.  But why
> >is comparing a rangefinder lens
> >to an SLR lens like comparing apples and oranges??  They do indeed
> >have different
> >focusing methods but how does that bear on lens testing?
> >
> >Mark H.
> >
>
> I don't know whether it is actually true or not, but it is said that
> rangefinder lenses are inherently superior to slr lenses.  The reason
> given is that is much more difficult to design and build a lens which
> has more physical distance from the back of the lens to the film
> plane to allow room for the slr mirror to flop around. That is one
> reason why slr lenses are usually much larger, heavier, with more
> elements than the equivalent rangefinder lens. So the SLR lens is, in
> a sense, a compromise to the viewing system rather than just making
> the best lens you can.  On a range finder you can even put the back
> glass of the lens up against the shutter curtain if that is the best
> place for it in the lens design.
>
> You can see some differences if you go to Photodo.com and compare
> similar MTF scores for equivalent Leica M and Leica R lenses.  For
> instance: 50/1.4 = 4.2(M), 4.3(R)[not here obviously]; 50/2= 4.6(M),
> 4.5(R); 35/2 = 4.1(M), 3.8(R); 35/1.4 = 3.8(R); 28/2.8 = 4.1(M),
> 3.8(R).
> On the other side of the argument you could say that a short distance
> to the film plane is only a factor on wide angle lenses and there is
> no inherent advantage to lenses of one focus system over another at
> other focal lengths.
>
> I do take MTF testing, at least on this site, with a grain of salt.
> I think the Zuiko 28/2 probably is better than 2.6 and better than
> the 200/4 which gets the same score.
> --
> Winsor Crosby
> Long Beach, California

I think among Leicaphiles (sp?) it is accepted that for a given GENERATION
of lenses the M's are in general SLIGHTLY superior in the short focal lengths
lenses for exactly the reasons you stated -- shorter lens registration distance 
and
design freedom of putting glass very close to the film plane if needed because
there is no mirror to clear.

There has been somewhat of a flurry of new M lens designs over the past decade
especially using Aspheric elements and/or going to faster glass in shorter 
focal lenghts
such as the 28mm F2.0 Summicron-M, 24mm F2.8 Elmarit-M and 21mm F2.8
Elamarit-M Aspheric lenses. Some of the R lenses are "overdue" for a 
recomputation to bring them up
to the same degree as their M counterparts.  But a (relatively) small outfit 
like Leica can only do
so much in a given time.

MTF testing, while not an end all, is still an extremely useful parameter for 
lens quality.
I work at Raytheon on FLIR (Thermal imaging) systems and believe you me, MTF is
a key parameter that is looked at in an optics design and in guaging image 
performance.

I think what might be a little strange is the way Photodo.com comes up with 
their "overall" number.
For any members that haven't done so, read the comments at the photodo.com site 
that explains MTF
and in particular how they come up with the values they do.  I usually
ignore the "overall" number and look at the 2 or more charts -- that tells much 
more of
the story.

Mark



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