[rollei_list] Re: changing lens formulas
- From: Carlos Manuel Freaza <cmfreaza@xxxxxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Sun, 4 Nov 2007 22:35:23 -0300 (ART)
Hi Eric:
It was an article written by two Zeiss
engineers with the tittle "Resolving Power and
Contrast" and published in the "Zeiss Information
Nº51", I have the URL for the only English version I
could find online, however this translation has the
text only, it does not show the photographs and
diagrams you can find in the original article, these
elements are very convincing to support the engineers
point of view:
http://www.pauck.de/archive/mailinglist/tech-3d/mhonarc/msg00544.html
All the best
Carlos
--- Eric Goldstein <egoldste@xxxxxxxxx> escribió:
> There is a famous Zeiss document which may account
> for this. It used
> to be up on the web but I have not found it for many
> years. It was a
> paper describing a pivotal decision for Zeiss... if
> I am remembering
> correctly, their research into end users revealed
> that resolution in
> excess of 40 lp/mm was seldom needed. As lenses
> could be apotised to
> favor either resolution or accutance/edge contrast,
> and it was the
> later which was the major factor in perceived
> "sharpness," they were
> moving in that direction. Just about every other
> major manufacturer,
> with the exception of Canon, followed.
>
> I used to have the doc as a pdf but have not been
> able to find it...
> perhaps Carlos knows of it and it's location...
>
>
> Eric Goldstein
>
> --
>
> On 11/4/07, aghalide@xxxxxxx <aghalide@xxxxxxx>
> wrote:
> >
> >
> >
> >
> > After 4 years at /RIT and two weeks working for
> the fashion editor of the
> > Ladies' Home Journal I was recommended by C.B.
> Neblette for a position at
> > Modern Photography Magazine to replace the
> technical person who left to
> > write books and brochures about Polaroid products.
> That was 1957. Upon
> > returning from 6-months active duty in Arkansas I
> worked with Optical Expert
> > Ben Sherman to create a lens testing method. Ben
> decided to use the U.S.
> > Airforce targets and test for resolution and call
> it lens sharpness.
> >
> > This worked most times, but failed manytimes.
> Zeiss lenses for the Zeiss
> > Contarex tested badly for resolution and great for
> sharp images. Zeiss
> > seemed to be designed to give high contrast, as
> did many Nikkors which also
> > failed in resolution. Minolta did well with
> resolution and fair with
> > contrast. Leica lenses did well in both cases. So
> we didn't publish low
> > contrast lenses because we were really testing for
> high and low resolution
> > not contrast. If the lens failed a test we didn't
> publish the results.
> >
> > Many years later they added contrast to the lens
> test. Ed Meyers
> >
> > -------------- Original message from "Richard
> Knoppow"
> > <dickburk@xxxxxxxxxxxxx>: --------------
> >
> >
> > >
> > > ----- Original Message -----
> > > From: "Douglas Nygren"
> > > To:
> > > Sent: Sunday, November 04, 2007 8:51 AM
> > > Subject: [rollei_list] Re: changing lens
> formulas
> > >
> > >
> > > > Interesting thread, this. Let me add a point
> or two.
> > > >
> > > > A friend with an old Zeiss lens showed me a
> mark next to
> > > > an F stop. He said that probably came from the
> factory. He
> > > > explained that at one point the factory would
> pre-test
> > > > lenses and mark the sweet spot. I don't know
> if that's
> > > > true or not.
> > > >
> > > > My experience with a relatively new Zeiss lens
> on a Contax
> > > > MF 645 was that one particular lens wa s disa
> ppointing
> > > > except at one certain F-stop, where it is
> terrific.
> > > > People have a three-dimensionality to them.
> > > >
> > > > Until I found that spot, I used to curse
> myself for having
> > > > bought it. Now I'm glad I did.
> > > >
> > > > Doug
> > > >
> > > Unless one has access to factory archives its
> almost
> > > impossible to tell what the prescription for a
> given lens is
> > > beyond its generic type. There are perhaps a
> dozen or more
> > > patents from Zeiss Jena on Tessar type lenses
> including a
> > > few clearly experimental ones and some others
> from C.Z. in
> > > Oberchoken. Add to this perhaps a hundred
> patents on Tessar
> > > types from other manufacturers and you have some
> idea of how
> > > difficult it is to identify a particular
> commercial lens as
> > > being a particular prescription. Also, not all
> design
> > > variations were patentable.
> > > It is certainly true that there was relatively
> poor
> > > quality control of lenses up to WW-2. That was
> improved by
> > > the major manufacturers in both the U.S. and
> Germany after
> > > the war because war-time work required that a
> higher
> > > standard be applied. However, there is still a
> lot of
> > > variation between individual samples.
> > > To evaluate a lens requires that the aerial
> image be
> > > examined. This eliminates a lot of variables
> such as all the
> > > mechanical problems of a camera and the
> variables introduced
> > > by film. It is not too difficult to see at least
> major
> > > faults in a lens this way. Tests made in a
> camera actually
> > > test the entire camera and are subject to
> inaccuracies in
> > > focus and variations in the film plane.
> > > There is a tremendous amount of rumor about
> lenses and
> > > their design, mostly without any means of
> substantiating it.
> > > Some of it makes no sense in light of the
> fundamentals of
> > > o ptics and design.
> > >
> > > ---
> > > Richard Knoppow
> > > Los Angeles, CA, USA
> > > dickburk@xxxxxxxxxxxxx
> > >
> > > ---
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