[rollei_list] Re: Tessar vs Tessar;
- From: Jerry Friedman <tinycameraco@xxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Fri, 12 May 2006 04:59:02 -0700 (PDT)
Once again, I find your explanation excellent. I was not aware of that great a
known diversity within the Tessar ranks. One Tessar that i have which is really
amazingly good is the B@L Tessar on a National Graflex II that I picked up a
while ago for fun. The lens lacks the contrast one would want in a modern lens
but it resolves well. The camera itself is really a trip. It is fun to use but
only for the masochist in me. How Graflex expected this camera to sell is
beyond me. It it, without a doubt, the slowest using camera that i have ever
used. But, folded up, it is compact..... I keep having this dream of a camera
about two inches on a side producing an imade about 6x6cm. Of course, before
that I was busy looking for a Minox that could produce a mural.
Jerry F.
> >
> I can say I have one not so good Tessar. Its a 161mm,
> f/4.5 in a barrel. It was so bad at first I thought the
> middle element might have been turned around. After
> re-assembling it a couple of times and making sure
> everything was really tight the performace was better but
> not up to other Tessars. I don't know what is wrong with it
> but suspect there may be a spacing error. Other Tessars I
> have are uniformly good.
> Zeiss made many variations of the Tessar. Included in the
> LensView program I mentioned before is the Zeiss Index. This
> was a compilation of lens designs assembled by Willie Merte,
> one of Zeiss's great designers. There are no dates on the
> entries in LensView but the list appears to have been
> started in the late Teens perhaps and carried up to about
> the beginning of WW-2. It incudes both Zeiss and other
> maker's lenses. Zeiss appears to have disassembled,
> measured, and calculated the performance of competitor's
> lenses. They vary, some are very good, some awful. Among the
> lenses included is a Tessar made for Kodak. If the computer
> analysis is to be believed its pretty awful. OTOH, the Kodak
> lenses analysed are quite good. Its quite possible the
> prescription for the Tessar made for Kodak is inaccurate,
> one would have to examine an actual sample of the lens to
> know.
> Zeiss kept playing with the Tessar design. Among other
> versions are a couple featuring aspherical surfaces. These
> appear to have exceptional performance, at least from the
> residual spherical aberration standpoint. Another curious
> thing is that Zeiss worked on the Dagor design extensively.
> Evidently, they felt that the Dagor and reversed Dagor had
> considerable potential.
> Of course, there is no way to know what the performance
> of these ancient lenses was like without setting them up on
> an optical bench and making tests. The analysis will not be
> as thorough as one made using a computer design program on a
> prescription but it will be of an actual lens, not just the
> potential of a design. One can at least measure the primary
> aberrations and get MTF curves. From the MTF curves some
> other characteristics can be estimated, for instance edge
> contrast.
>
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@xxxxxxxxxxxxx
>
> ---
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