Re: Polarising Filter Question

[Jim Brick <jim@brick.org>]

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. 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. 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.
Otherwise use an external meter and add a factor of 2.3 (no polarizing
effect) to 2.8 (full polarizing effect). The linear polarizers will give a
greater effect under certain conditions, but your meter won't work. The
meter beam splitter basically polarizes the light on the way to the meter
cell. A linear polarizer adds a second polarizer which will block light
from getting to the meter. The circular polarizer uses an additional 1/4
wave retarder foil which fools the meter beam splitter thus allowing the
meter to see unpolarized light for a reading. Use circular polarizers so as
not to add yet another level of complication to your fun.

Jim