"R.S. Adams" <aeolian@xxxxxxxxxxxxxx> moved upon the face of the 'Net and spake
thusly:
> Okay, gang. . . here's the dumb question of the month. What is the
> practical difference between a circular and linear polarizer? Is there
> a difference in the effect produced? The amount of light attenuated?
> Both? Neither? What's the story. I've have not used a PL in a long
> time (more than I care to admit) -- I need to buy a couple and want to
> get the straight scoop.
OK.
Polarizing screens (aka linear polarizers) block all waves except
those in a certain plane.
Some TTL metering systems use beam-splitters and/or half-silvered
mirrors to redirect some of the incoming light to the meter.
If the light is plane-polarized, it disrupts the function of the beam
splitter.
Using a linear polarizer on such cameras will send your metering to
shit.
A "Circular Polarizer" consists of an ordinary polarizing screen,
followed by a "quarter wave plate" which "depolarizes" the light.
The effectively unpolarized light will then behave OK in the metering
system.
So if you use a PL (linear) filter, the light is polarized all the way to film,
but with a PC (circular) filter the polarized light gets "scrambled"
again after passing the screen.
HTH,
Chris.
--
chris@xxxxxxxxxxxxxx, when he visits the Real World, is Christopher J. Biggs
Stallion Technologies, Australia. Ph. +61-7-3270-4266 Fax. +61-7-3270-4245
I dig PGP, MIME and Rush. Send mail with "Subject: sendpgpkey" for my pubkey
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