Polarizer(s) questions

Discussion in 'Digital Photography' started by Eric Miller, Aug 4, 2011.

  1. Eric Miller

    Eric Miller Guest

    Is it necessary to use a circular polarizer with contrast detect auto-focus?

    If so, would two circular polarizers work for a variable ND filter on
    such a camera? (Just for indoor portraits, web resolution)

    Eric Miller
    www.dyesscreek.com
    Eric Miller, Aug 4, 2011
    #1
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  2. Eric Miller

    nospam Guest

    In article <j1cta0$5al$>, Eric Miller
    <> wrote:

    > Is it necessary to use a circular polarizer with contrast detect auto-focus?


    circular polarizers are only required if there's a beam splitter in the
    optical path.

    > If so, would two circular polarizers work for a variable ND filter on
    > such a camera? (Just for indoor portraits, web resolution)


    use one circular and one normal, with the circular polarizer closest to
    the camera.
    nospam, Aug 4, 2011
    #2
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  3. Eric Miller

    PeterN Guest

    On 8/3/2011 9:39 PM, Eric Miller wrote:
    > Is it necessary to use a circular polarizer with contrast detect
    > auto-focus?


    Generally yes. While some autofocus systems will work with a linear
    polarize, you should test your system.

    >
    > If so, would two circular polarizers work for a variable ND filter on
    > such a camera? (Just for indoor portraits, web resolution)


    I use a circular + a linear with the circular closest to the lens. the
    disadvantage is that you don't get true neutral density, you will lose
    some specular highlights that you want in your image. But the cost is
    substantially less than a variable ND filter.

    --
    Peter
    PeterN, Aug 4, 2011
    #3
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