T3D Circular Polarizers (fwd)

[E R Swanson <ers@xxxxxxxxxxxxxxxxxxxx>]

Some info a friend sent me re circular polarizers...

--Elliott

> 
> 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.
> 


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