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Re: [OM] Help! Light theory, cp-l

Subject: Re: [OM] Help! Light theory, cp-l
From: "Jim L'Hommedieu" <lamadoo@xxxxxxxx>
Date: Tue, 28 May 2002 00:27:05 -0400
I thought the pattern in a circular polarizer is circular, that is,
concentric circles, sharing a common center.  So the inner most circle has a
very small diameter, and each successive circle, surrounding its
predecessor, is slightly bigger.  Rotating such a circular polarizer has no
meaning, unless the centers don't match the center of the lens axis.

I would guess by extension that combining two circular polarizers of
identical spacing between the rings would, in theory, overlap perfectly,
resulting in a darker image.  In reality, I imagine that the centers of BOTH
polarizers would be slightly askew from the center axis, resulting in "hot
spots" in light arcs.

Considering the horrific cost of circular polarizers, it seems like the most
expensive possible way to get neutral density.  (I bought my 55mm CPL in a
shop instead of mail order and it was $40 USD.  Ouch!  Worst of all, I've
opened it.)

Lamadoo




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