Christopher Biggs wrote:
BTW, it does not sound like a dumb question at all.
If the circular polarizer only passes light on a certain plane and then
a 1/4 wave disrupter rescrambles the light, it kind of sounds like an
expensive UV filter. You still end up with scrambled light like you
started with minus the UV. Enlighten me, where am I missing the boat
with this definition ?
<><><><><><><><><><><><><><
>
> "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.
>
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