Archived posting to the Leica Users Group, 1996/06/12

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To: leica-users@mejac.palo-alto.ca.us
Subject: Re: Swing-out polarizer
From: Eric Welch <ewelch@gp.magick.net>
Date: Wed, 12 Jun 1996 14:50:21 -0700

At 10:44 PM 6/12/96 +0300, you wrote:

>described mechanically, but I got one question
>concerning the optical quality. Is it OK, if the filtering
>effect is not "uniform"? If I look the sky through it,
>there is not filtering effect at the center of the filter -
>except in the very center. The size of the "white

You have to realize the way a polarizer works is not going to give you a
uniform effect. The reason is, the amount of polarization differs depending
on how far off axis from the light source you are looking. The maximum
effect will happen at 90 degrees from the light source. Of if the sun is in
the east, the greatest effect will be pointing north and south. And the
closer you get to the light source (or 180 degrees from that) the less
polarization occurs. 

And just to make it clear, when the sun is directly overhead, the greatest
effect will be anywhere on the horizon. Does that help?

==========================
Eric Welch
Grants Pass Daily Courier


Replies: Reply from Wolfgang Sachse <sachse@msc.cornell.edu> (Re: Swing-out polarizer)