Archived posting to the Leica Users Group, 1996/10/12

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Subject: Re: Non-Polarising Summitar Polariser?
From: Willem-Jan Markerink <w.j.markerink@a1.NL>
Date: Sun, 13 Oct 1996 02:08:08 +0000
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Priority: normal

On 12 Oct 96 at 10:56, Nick Jackson wrote:

> I wonder if anyone of you can unravel a small mystery for me.
> I just bought,via mail order ( a necessity from here), a polarising
> filter for a 50mm summitar from a dealer in London.  The filter arrived
> in a beautiful little Leitz leather purse and showed great promise on
> first sight.  It has some signs of fungus growth around the very edge
> which I presume is in the middle of the sandwich of glass, but what is
> most bizarre is it doesn't appear to have any polarising effect!
> Now either I'm going blind or its simply lost its ability polarise - is
> this possible?  
> At certain angles to the light faint parallel lines are just visible, so
> I'm fairly sure it is polarising glass and hasn't been swapped.  I know
> the shop and they are very reputable.  I will send it back and wait for
> another to appear, but would be grateful for any explanation of this
> anomoly.
> Nick Jackson

Polaroid material ages over time. I have never seen it myself, but a 
friend did. Heat and humidity apparently accellerate this process. 
Note that the environmentally sealed Kaesemann quality (sold by B+W 
and Heliopan) at least tackles the humidity problem. Not sure 
whether moisture is worse than heat, but I have seen warnings for 
Somewhere in the back of my mind I have the faint idea that pol
materials use organic could explain this aging....not
sure though.
Maybe you should post this on the newsgroup sci.optics....


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      The desire to understand 
is sometimes far less intelligent than
     the inability to understand

[note: 'a-one' & 'en-el'!]