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Thread: Identifying Cir-Polarizer stops

  1. #1

    Default Identifying Cir-Polarizer stops

    Hi guys,

    How do you identify how many stops down does a Cir-polarizer produce?
    Is there a marking or something? or there is only one kind of polarizer ?

    Sorry if the question sounds stupid... new to polarizers ... hehe


  2. #2
    Senior Member
    Join Date
    Mar 2004
    lulu island


    not sure how many or how much.
    given a contant lighting environment, you meter a spot without the filter and another with the filter, then the difference will be the answer.
    hope i'm right.

  3. #3


    OOPS... I thought I answered it but somehow the post didn't came up...

    It should be slightly more than 1 stop of light loss, if the incident light is circularly polarized(isotropic). (Ideally it is 1 stop but there's always extra losses here and there. )
    However, light reflected off non-metalic surfaces are ovally polarized, meaning the intensity of EM wave is different in different directions. And how 'oval' the light is depends on the incident angle of that reflected light beam - and the ovality and direction of your PL front plate determines how many stops are lost.

    Drudkh - good point it's tested to be slightly over 1 stop with a Hoya 67mm CPL, against a blank wall.
    Last edited by grantyale; 29th April 2005 at 01:45 AM.

  4. #4




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