[rollei_list] Re: Whiteface T with Xenar question
- From: Marc James Small <marcsmall@xxxxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Thu, 19 Mar 2009 00:12:26 -0400
At 11:51 PM 3/18/2009, Sanders McNew wrote:
Carlos and Richard, thanks for your replies. Carlos, are you
certain about your statement that the Tessar and the Xenar
must be identical because F+H's requirements were the
same? In this instance I'm not so sure of that.
Sanders
It is not as simple as you suggest.
First, Zeiss recomputed the entire Tessar range
in the late 1950's. This was primarily done for
use on the Contaflex SLR's -- the recomputed
Tessars appear on the Super B, Super BC, and S --
but the improved design was extended to the
Rolleiflex T. As the recomputed lens appeared in
1962 and the T in 1958, I would suggest that
early T's had non-recomputed lenses.
The recomputing was done under the direct of Dr
Hans Sauer. Sauer had come up at Carl Zeiss Jena
as the protege of Dr Ernst Wandersleb, who
himself had been the protege of Dr Paul Rudolph,
the designer of the Tessar. Wandersleb spent
four decades in working to improve the Tessar and
Sauer was part of the last decade or so of
that. So, there is a direct link from the
original Tessar design. Sauer also designed the
five-element Planar as used in the Rolleiflex
TLR's and the early Planars for the Hasselblad SLR.
By 1970, Zeiss was desperate to get out of the
production of photographic lenses, as they made
far more profit from military, industrial,
medical, and scientific gear. Thus, when F&H
decided to make a final run of T's to meet a
contract with the Royal Navy, CZ declined to
produce any more Tessars, and F&H then turned to
JSK who produced the Xenars in question for that last batch of T's.
Carlos is correct in saying that F&H would
establish minimum quality requirements and that
the Xenar must have met them as well as did the
CZ Tessar. But that does not mean that the
Tessar did not exceed these requirements. I
would doubt it: JSK is a company who does not
make mediocre lenses (well, they DO, but at
Göttingen at their ISCO works). I see no reason
to believe that the recomputed Tessar and the
contemporary JSK Xenar were not on a par in terms
of optical performance. But I do not KNOW this
as I have never seen any test results such as MTF charts.
Thanks to the courtesy of Bill Lurie from the
ZICG, I was recently gifted with a copy of the US
National Bureau of Standards Special Publication
374, METHOD FOR DETERMINNG THE RESOLVING POWER OF
PHOTOGRAPHIC LENSES (June, 1973), which includes
some really nifty resolution charts far superior
to the USAF charts we all know -- the charts
themselves were drawn in 1952 and were printed by
the US Bureau of the Mint on engraving
presses. But I've been laid up with some sort of
head virus and haven't tested anything yet. And
I have no version at all of a T, so I wouldn't be able to help, in any event.
Marc
msmall@xxxxxxxxxxxx
Cha robh bàs fir gun ghràs fir!
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