[rollei_list] Re: Planar vs. Xenotar test
- From: Jerry Lehrer <jerryleh@xxxxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Mon, 10 Jan 2005 14:45:07 -0800
Mike,
After using Rollei TLRs since 1947, I have learned that
there is no difference in the results comparing Xenars to
Tessars, or Planars to Xenotars. There are "camps" of
fanatics that attribute magical properties to some of these
names. For your own sanity, ignore them! Just take
pictures.
Jerry
"michael Sta. Maria" wrote:
> Peter,
> Thanks for the reply. All of this rollei lens
> comparison is almost making me go MAD... Since it is
> my first Rolleiflex I am becoming neurotic about
> certain things like lens elements, which lens has the
> best bokeh (I've actually read that the number of
> blades in the diaphragm have something to do with it.
> Conversely there are people that say it doesn't have a
> thing to do with it wide open), film flatness, 'Flex
> vs. 'Cords. Blah, blah, blah. All in all as long as
> I have a good lens that works when I trip the shutter,
> then that is all that matters. But it's always nice
> to know that I own high quality, classic and timeless
> equipment.
> MIKE...
>
> --- dkhong@xxxxxxxxxx wrote:
>
> >
> > Thanks Richard for a really in depth account from a
> > really knowlegeable
> > person. I suppose stopping down is the most
> > appropriate way to achieve
> > sharpness and contrast.
> >
> > Dan K.
> >
> >
> >
> >
> > "Richard Knoppow"
> > <dickburk@xxxxxxxxxxxxx>@freelists.org on 10/01/2005
> > 08:59:24 AM
> >
> > Please respond to rollei_list@xxxxxxxxxxxxx
> >
> > Sent by: rollei_list-bounce@xxxxxxxxxxxxx
> >
> >
> > To: <rollei_list@xxxxxxxxxxxxx>
> > cc:
> > Subject: [rollei_list] Re: Planar vs. Xenotar
> > test
> >
> >
> > ----- Original Message -----
> > From: "Peter Kotsinadelis" <peterk727@xxxxxxxxx>
> > To: <rollei_list@xxxxxxxxxxxxx>
> > Sent: Sunday, January 09, 2005 12:26 PM
> > Subject: [rollei_list] Re: Planar vs. Xenotar test
> >
> >
> > > Hi Mike,
> > >
> > > We joke a bit about Planar v. Xenotar and Tessa v.
> > Xenar.
> > > It has been
> > > an ongoing battle here on this list and another.
> > Both the
> > > Planar and
> > > Xenotar are excellent. The major difference
> > between the
> > > two is the
> > > Planar is slightly better wide open. This is
> > arguable and
> > > those who
> > > prefer the Xenotar will say otherwise. The Xenotar
> > and
> > > other Schneider
> > > lenses are slightly more contrasty than the
> > Planar. I own
> > > both.
> > > As to the Tessar, it is soft until about F5.6 then
> > at F8
> > > and F11 its
> > > resolution is equal to that of the Planar and
> > Xenotar and
> > > sometimes a
> > > tad better in the center than the edges. Same for
> > the
> > > Xenar, a
> > > Schneider copy of the Tessar. That is the primary
> > > difference with
> > > Tessar v. Planar in that the Planar is more even
> > in
> > > sharpness
> > > edge-to-edge.
> > >
> > > Peter K
> > >
> > I will have to arrange to have two lady friends,
> > Tessa
> > and Xena, to carry my equipment around. Both will
> > have nice
> > boquets but one will be flowery and the other spicy.
> > All
> > four of their elements will be well designed.
> > The Tessar as a generic type suffers from oblique
> > spherical which can not be completely corrected for.
> > Modern
> > glass does not make a significant difference. The
> > Xenotar
> > type, despite looking as though its asymmetrical,
> > actually
> > has a lot of symmetry which makes correcting it for
> > coma,
> > lateral color, and geometrical distortion much
> > easier. These
> > three aberrations are cancelled by symmetry. The
> > lack of
> > coma and better oblique SA make these lenses much
> > better
> > performers than a Tessar when wide open. SA and coma
> > are
> > proportional to the stop so stopping down a lens
> > reduces
> > these aberrations rather quickly. Oblique SA is also
> > proportional to the stop. The _usable_ speed of a
> > Xenotar is
> > significantly greater than that of a Tessar of the
> > same
> > nominal speed.
> > Bokay seems to be a function of the balance of
> > higher
> > order aberrations. Lenses can be perfectly sharp for
> > in
> > focus images but have somewhat odd looking out of
> > focus
> > images. Fast lenses, where the high order
> > aberrations are
> > more promenent than in slower lenses, probably have
> > more
> > trouble with this.
> > Arguing about Tessar vs: Xenar is hopeless since
> > they
> > share certain characteristics and neither is a
> > unique
> > design. Zeiss has made many variations of the basic
> > Tessar
> > design as Schneider has for their version of it. Its
> > pretty
> > hard to know exactly what prescription applies to
> > which
> > production lenses. The same for the Xenotar vs:
> > Planar.
> > Zeiss made at least two variations of the five
> > element
> > Planar. The original appears to have been very
> > difficult to
> > make. The later version is constructed more like the
> > Xenotar. The very limited data in the lens survey
> > program
> > LensVIEW suggests that the original Planar (with
> > cemented
> > front element) is the best of the group, but not by
> > very
> > much. Its steeply curved, closely spaced, elements
> > would
> > have made it a fussy lens to manufacture. I suspect
> > the
> > change to the Xenotar type, which has thicker
> > elements and a
> > plane cemented surface, was for reasons of
> > economical
> > production rather than performance.
> > Sometime someone, with time to burn, will obtain
> > several
> > samples of each of these lenses and test them with
> > modern
> > lens testing equipment. This will generate genuine
> > MTF
> > curves, defocus curves, etc., to compare with the
> > computer
> > analysis of the prescriptions, provided one can be
> > sure of
> > published prescriptions.
> > There are indictions in the Zeiss Index that back
> > in the
> > old days Zeiss obtained competitor's lenses and
> > measured the
> > actual prescriptions. This would require
> > disassembling the
> > lens, measuring the curvature and thickness of the
> > elements,
> > and, their glass characteristics. This last is no
> > easy
> > chore.
> > Measuring lens performance either by visual
> > inspection of
> > the aerial image or in film, is fraught with
> > potential
> > errors. I suspect that most of the tests in popular
> > magizines would leave much to be desired in the way
> > of
> > design and control of the experiment so I am always
> > a bit
> > sceptical of the published results.
> >
> > ---
> > Richard Knoppow
> > Los Angeles, CA, USA
> > dickburk@xxxxxxxxxxxxx
> >
> >
> >
> >
> >
> >
> >
> >
>
>
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