[Leica] Report Vario-Elmar 35-70, part 1a

[Erwin Puts <imxputs@knoware.nl>]

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The economics and physics of optical design allow for several strategies.
One can design lenses with relative small apertures (around f/4 and
smaller) quite cheaply with very decent performance. One can also design
lenses with wider apertures  and produce them  in a lowcost manner when one
is prepared to allow for wider production tolerances and cheaper materials.
The third strategy is to build wide aperture lenses with a very high level
of performance and use high quality materials. The economics then are
unforgiven and a steep price is the result.

Given the craft and techniques of optical design nowadays several older
notions have to be scrapped from a working photographers mental notebook.
For a long time the vested opinion had it that zoomlenses could never beat
the best fixed focal length lenses. This is not true anymore as the report
of the Vario 35-70 will try to prove.
It has been a truism to assume that wider aperture lenses, because of a
more sophisticated design would be capable of better imagery than smaller
aperture lenses of the same focal length.
Again this is not true anymore as a universal rule.
The step from a f/4 lens to a  f/2,8 is a major design problem and the step
from f/2,8 to f/2 even more so. The argument for this state of the art view
is partly exposed in my Summilux-R 1,4/50 report. The luminous energy
flowing through a lens of aperture f/2,8 is twice the amount of a lens with
an aperture of f/4 and the effort to control and manage this energy flow is
very demanding.  It is not well recognized how difficult it is for a
designer to control aberrations when stepping up one stop. Many aberrations
grow in magnitude with a cube power when the aperture is doubled. And that
is quite hefty.
A third truism is the notion that a lens can be designed for contrast or
resultion. Again this notion has had in the past very limited validity and
is now obsolete.

In the recent past a well designed wide aperture lens could hold its own
against smaller aperture versions, because these versions most often
belonged to the first type of strategy outlined above.
The Vario-Apo-Elmarit-R 1:2,8/70-180mm showed within the Leica stable that
excellent performance is indeed possible with a zoom, as good as or even
surpassing fixed focal length lenses. In the M line the Tri-Elmar makes the
same point. (even if this one techniqually is not a zoom).

The object of this report is the Vario-Elmar-R 1:4/35-70, introduced in
1997. It is designed in Solms and built in Japan, has 8 lenses, of which
one surface is aspherical. The newer 2.8/35-70 has 11 lenses, many of which
are of exotic specification, proving the effort to go up just one stop.
With this lens Leica introduces a fourth strategy and that is building a
low aperture lens to very high optical standards of performance. With a
weight of 500 grams it is half the weight of the 2.8/35-70 and  equal the
weight of the new Apo-Summicron-M 2/90 ASPH.
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<fontfamily><param>Times</param>The economics and physics of optical
design allow for several strategies. One can design lenses with
relative small apertures (around f/4 and smaller) quite cheaply with
very decent performance. One can also design lenses with wider
apertures  and produce them  in a lowcost manner when one is prepared
to allow for wider production tolerances and cheaper materials. The
third strategy is to build wide aperture lenses with a very high level
of performance and use high quality materials. The economics then are
unforgiven and a steep price is the result. 


Given the craft and techniques of optical design nowadays several older
notions have to be scrapped from a working photographers mental
notebook. 

For a long time the vested opinion had it that zoomlenses could never
beat the best fixed focal length lenses. This is not true anymore as
the report of the Vario 35-70 will try to prove.

It has been a truism to assume that wider aperture lenses, because of a
more sophisticated design would be capable of better imagery than
smaller aperture lenses of the same focal length. 

Again this is not true anymore as a universal rule. 

The step from a f/4 lens to a  f/2,8 is a major design problem and the
step from f/2,8 to f/2 even more so. The argument for this state of the
art view is partly exposed in my Summilux-R 1,4/50 report. The luminous
energy flowing through a lens of aperture f/2,8 is twice the amount of
a lens with an aperture of f/4 and the effort to control and manage
this energy flow is very demanding.  It is not well recognized how
difficult it is for a designer to control aberrations when stepping up
one stop. Many aberrations grow in magnitude with a cube power when the
aperture is doubled. And that is quite hefty.

A third truism is the notion that a lens can be designed for contrast
or resultion. Again this notion has had in the past very limited
validity and is now obsolete.


In the recent past a well designed wide aperture lens could hold its
own against smaller aperture versions, because these versions most
often belonged to the first type of strategy outlined above.

The Vario-Apo-Elmarit-R 1:2,8/70-180mm showed within the Leica stable
that excellent performance is indeed possible with a zoom, as good as
or even surpassing fixed focal length lenses. In the M line the
Tri-Elmar makes the same point. (even if this one techniqually is not a
zoom).


The object of this report is the Vario-Elmar-R 1:4/35-70, introduced in
1997. It is designed in Solms and built in Japan, has 8 lenses, of
which one surface is aspherical. The newer 2.8/35-70 has 11 lenses,
many of which are of exotic specification, proving the effort to go up
just one stop.

With this lens Leica introduces a fourth strategy and that is building
a low aperture lens to very high optical standards of performance. With
a weight of 500 grams it is half the weight of the 2.8/35-70 and  equal
the weight of the new Apo-Summicron-M 2/90 ASPH.</fontfamily>

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