I see your point Moose, and have thought long and hard about it,
but I think it is not relevant (though clearly correct) to say the
factor varies.
Sure, a polarizer will have a variable effect on the average meter
reading (ignoring for the moment the OM-4 semi-silvered specifics).
But in removing specular highlights from the average meter reading
(using a polarizer), surely all you are doing is eliminating what
would otherwise be underexposure of the rest of the frame? Of course,
you would then lose the detail in the reflected highlights - but if
you wanted the detail in those highlights, you wouldn't have used a
polarizer in the first place.
Do you see my point?
What I am missing?
Piers
-----Original Message-----
From: owner-olympus@xxxxxxxxxxxxxxx [mailto:owner-olympus@xxxxxxxxxxxxxxx]
On Behalf Of Moose
Sent: Friday, March 14, 2003 10:09 AM
To: olympus@xxxxxxxxxxxxxxx
Subject: Re: [OM] Reviewing the Basics of PL's with OM-4
--snip
However, you are both assuming that the filter factor of a polarizer is
constant and that is incorrect. The nominal filter factor is correct
where there is no polarized light to filter. Any polarized light removed
by the filter increases the filter factor by an unknown amount. Think
about it. Metering without the filter, your meter measures all that
nasty glare off the water (or whatever). With the polarizer on and
adjusted to minimize the glare, one of the brightest sources in the
scene is gone and the adjustment for correct exposure can easily be over
2 stops. Put a polarizer on a camera without a partially silvered mirror
exposure system or over a manual meter, rotate it while watching the
meter with different scenes and you'll see the effect.
--snip
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