Archived posting to the Leica Users Group, 1996/10/12
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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
both.
Somewhere in the back of my mind I have the faint idea that pol
materials use organic elements....it could explain this aging....not
sure though.
Maybe you should post this on the newsgroup sci.optics....
- --
Bye,
_/ _/ _/_/_/_/_/ _/_/_/_/_/
_/ _/ _/ _/ _/ _/ _/
_/ _/ illem _/ _/ an _/ _/ _/ arkerink
_/_/_/
The desire to understand
is sometimes far less intelligent than
the inability to understand
<w.j.markerink@a1.nl>
[note: 'a-one' & 'en-el'!]