[rollei_list] Re: Lens coatings and veiling flare.
- From: Carlos Manuel Freaza <cmfreaza@xxxxxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Thu, 9 Jul 2009 16:56:21 -0700 (PDT)
My 1954 2.8/80 Xenotar lens coating shows four little holes in the front
element coating layer, they are visible according the light angle and placed
very close to the upper left lens edge, they couldn't affect the image quality,
otherwise the coating looks good showing strong purple and blue-violet
reflections according the light, I know several old Xenotars have more serious
coating conditions problems.
I can't see any significant flaw in my 1954 Rolleicord IV Xenar coating, the
coating does not show the purple tint reflection you can see in the Xenotar, it
only shows a blue-violet reflection.
My 1964 3.5F Zeiss Planar six elements shows a double layer coating for each
lens surface clearly, one layer has a blue to violet-blue color reflection and
the other layer has a golden reflection, the coating condition looks very good
really.
BTW, as Marc explained yesterday, there were improvements about the single
layer lens coating along the years, f.e. materials selection and mixing, vacuum
chamber quality and temperature degree and temperature control among several
other factors. Improvements tended to increase lenses coatings durability and
hardness and then you can expect that a newer coating is harder than an older
one, of course.
Carlos
--- El jue 9-jul-09, Peter K. <peterk727@xxxxxxxxx> escribió:
> Schneider too. Very soft coatings on
> the Xenotars that were on the 50s
> TLRs. (Except for those of course that users here own, they
> are
> perfect.)
>
> On Thu, Jul 9, 2009 at 1:06 PM, Richard Knoppow<dickburk@xxxxxxxxxxxxx>
> wrote:
> >
> > ----- Original Message ----- From: "Ellestads" <ellestads@xxxxxxx>
> > To: <rollei_list@xxxxxxxxxxxxx>
> > Sent: Wednesday, July 08, 2009 7:52 AM
> > Subject: [rollei_list] Re: Lens coatings and veiling
> flare.
> >
> >
> >> Please be careful cleaning interior surfaces of
> older coated lenses. Many
> >> of
> >> theses lenses (including Leica) ued soft coatings
> on the inner elements.
> >> Cleaning can reduce those coatings.
> >>
> >> Tim
> >
> > Kodak certainly used soft coatings on some early
> coated lenses. These
> > were premium lenses made beginning in about the late
> 1930s. I don't know
> > what process was used to coat them but the coatings
> are _only_ on protected
> > inner surfaces and are very delicate.
> > While Marc beleives that Smakula, of Zeiss,
> invented hard coating I am
> > not so sure. Zeiss may have had this technology but
> the record seems to show
> > it was developed by a reseach group in the US during
> WW-2. Vacuum coatings
> > can be relatively soft and the early ones were. What
> was developed here was
> > the technique of baking the coatings in vacuo.
> Previously the coated lenses
> > were removed from the vacuum chamber and baked in a
> separate operation.
> > Baking in the coating chamber results in coatings
> nearly as hard as the
> > glass.
> > This method was developed as part of a research
> project for military
> > optics. I don't know what instruments or devices it
> was applied to. The
> > familiar Bausch & Lomb Navy binoculars appear to
> have been coated after
> > manufacture.
> > There is a good history of hard coating available
> at the Society of
> > Vacuum Coaters web site:
> > http://www.svc.org/
> >
> > Hard coating appears to have become available for
> civilian optics about
> > 1946. Kodak and Wollensak seem to have been among the
> first to offer coated
> > lenses. Some smaller manufacturers, Goerz for
> instance, evidently had to
> > farm out their coating and were among the last to
> offer it. Its much more
> > difficult to determine what technology was available
> in Europe. Keep in mind
> > that nearly all European industry was seriously
> disrupted by the war and
> > took some time to recover thus its possible that Leitz
> and others were using
> > older soft coating technology for a time.
> > This history of lens coating goes back a long
> way. H.D.Taylor, the
> > inventor of the Triplet, was one of the first to
> recognize that flare
> > reducing coatings were possible but he was never able
> to devise a practical
> > method of coating. Resarch was carried out at many
> places including Zeiss
> > and some curious ones like RCA. Smakula evidently was
> the first to realize
> > that vacuum deposition (c.1935) was an excellent way
> of creating uniform
> > coatings but those early coatings were not very
> durable. However, they were
> > much better than chemical dip coatings of the type
> being developed at RCA.
> > Those coatings will wipe right off the glass surface.
> >
> > --
> > Richard Knoppow
> > Los Angeles, CA, USA
> > dickburk@xxxxxxxxxxxxx
> > ---
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> >
>
>
>
> --
> Peter K
> Ó¿Õ¬
> ---
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