A "circular" polariser has two polarisation layers. The front layer is a
standard linear polariser. The back layer depolarises the light that passes
thru the front layer.
Why? Because the semi-silvered mirror that lets light thru to the meter cell is
sensitive to the polarisation of the light. So in some polarisation
orientations, more light will get thru, in others less light. In other (sigh)
cameras, this light is also used for the auto focusing & interferes with that.
Of course, if you use Off The Film (non-spot) auto metering in the OM-2s or OM-
4, it won't matter to the exposure. But the shutter speed display won't be
accurate. And if you use the spot metering, or the average in the OM-3, the
meter may not give you the correct exposure.
> Date: Tue, 4 May 1999 18:53:22 -0700
> From: Jan Steinman <jans@xxxxxxxxxxx>
> Subject: Re: [OM] OM3 and polarizers
>
> >From: "John A. Prosper" <prosper@xxxxxxxxxxxxxxxxx>
> >On Tue, 4 May 1999, Jan Steinman wrote:
> >|>> From: aclaudiomolinari@xxxxxxxxxxxxxxxxxxxxxx
> >|>> I read that with OM3 it's better to use circular polarizers: is it
> >true? | |>From: "Tom Trottier" <infoanim@xxxxxx> |> |>Yes. The OM2s & up
> >need to use circular polarisers... | |I think "need" is an overstatement
> >here. You can get away with a linear |polarizer if you are careful to
> >peak the meter reading with the polarizer...
> >A circular polarizer is only required for spot metering operations
> >which employs the beam splitter.
> I think "required" is an overstatement here. :-)
>
> My point is that any problems introduced by linear polarizers are
> detectable and correctable at the time you make the picture. If you have a
> linear polarizer and don't want to shell out the bucks for a circular one,
> you can make do.
>
> : Jan Steinman <mailto:jans@xxxxxxxxxxx>
------------------
From: Tom Trottier, President, ACT Productions Inc.
infoanim@xxxxxx http://www.act.ca
+1 613 594-4829 fax +1 613 594-8944
199 Holmwood Ave, Ottawa, Ontario, Canada K1S 2P3
"Make it as simple as possible, but no simpler" - Einstein
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|