P3D Re: (circular polarizers)

["William J. Carter, Ph.D." <wc@xxxxxxxxxxxx>]

At 03:32 AM 10/26/98 -0700, Peter Homer wrote:

>...  I believe one of them mentioned that
>there was an even greater light loss than with linear. 
Not too likely, as a circular polarizer is a linear polarizer coupled to a
clear retarder.
The retarder isn't a filter, per se, it just changes the characteristics of
the polarization. (Same as sugar water :)

>I am not shure what
>you mean by  "can I use circular ones  only in one direction?" but you will
>need both directions of rotation for stereo projection.
Present day commercial retarders are made from stressed polyvinyl acetate
(PVA). I do not think if they come in left or right "handedness". They do,
however, come in 1/4, 1/2, and 3/4 wave retardations. A 1/4 and a 3/4 wave
retarder would have the effect you're looking for, as would probably a 1/2
wave and straight linear.

> The only sources of the material I can think of are the computer and
>camera filters both expensive but you get quite large sheets with the
>computer filters but I dont know if you could get both rotations this way.
I buy the stuff in 1' x 1' sheets, from Polaroid.


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