Archived posting to the Leica Users Group, 1997/08/19
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On 18 Aug 97 at 17:56, Jim Brick wrote:
> At 08:25 PM 8/18/97 -0400, you wrote:
> >Dear Fellow LUGnuts,
> >
> >Now that I am using R lenses in addition to M lenses, I am getting
> >interested in using a polaroid filter. I have previously used circular
> >polaroid filters so that I could meter more easily with metering systems
> >that contained beam splitters. I understand that there is a way you can
> >use a linear polaroid filter but I found the circular polaroids easier to
> use.
> >
> >Now in my investigation of circular polaroid filters, I have discovered the
> >Kaesemann circular polaroid filters. They are even more expensive than the
> >normal B+W filers. Does anyone know the advantages of the Kaesemann
> >polaroid filters?
> >
> >Thanks. I'm having a lot of fun with the new 35-70 R zoom lens from Leica.
> > Can't wait to ge the winder.
> >
> >Richard
>
> Kaesemann circular polarizers are made with greater care making sure that
> the glass is absolutely flat and it is hermetically sealed.
A bit more on this otherwise correct statement: the glass is grounded
after sandwiching&sealing the polaroid foil inbetween. The foil is
also stretched to assure absolute flatness (I have an old brochure of
the Kaesemann factory (not B+W at that time), mainly stressing this
stretch & seal quality, as well as perfect polarisation).
There is also a downside to this sealing, as the process requires
excessive heat, which prevents glass coating after flat-grounding the
glass....coating requires even more heat (the more heat the better it
sticks to the glass I believe). So Kaesemann and multicoating are
mutually exclusive.
> Kaesemann
> filters were designed for use with fast long lenses and APO's because they
> are very sensitive to optical flatness and purity of filters.
Tele lenses, yes, but APO doesn't require more quality than non-APO.
> This will be
> keenly apparent on the 180 3.4 APO. If you want the best and never worry
> about if your filter is causing a problem, get Kaesemann polarizers. If you
> want to use your built-in meter, get Kaesemann circular polarizers.
I first read this wrong, so to avoid confusion: you want a *circular* pol
for built-in meters, not especially a Kaesemann circular.
- --
Bye,
Willem-Jan Markerink
The desire to understand
is sometimes far less intelligent than
the inability to understand
<w.j.markerink@a1.nl>
[note: 'a-one' & 'en-el'!]