Archived posting to the Leica Users Group, 1998/06/10

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Subject: [Leica] The Polarizer Problem
From: Frank Dernie <FrankDernie@compuserve.com>
Date: Wed, 10 Jun 1998 13:48:15 -0400

The recent posts on polarisers have made me think a bit more about the
Leica swinging hood. I use mine infrequently but had always assumed that
the device swung through 180 degrees so that the view seen through the
viewfinder was corrected for the film (inverted image on film) I had
assumed this 180 deg swing was therefore crucial. All suggestions made on=

the LUG for alternatives were ways of orientating filters on the lens at
the same angle as that shown by a direct view through the viewfinder, ie
180 degrees wrong on the film. Then I thought perhaps polarisers repeat
every 180 deg, given the physics of polarised light. Is this so and in th=
is
case why do Leica go to so much trouble to rotate the filter correctly in=

their swinging device? Also, on another tack what is a circular polariser=
?
If orhtogonality of polarised light is required for cancellation as I
understand it what is a circular polariser doing and how does it , for
example cancel a reflection?
Only Curious
Frank