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  1. #1

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    Stop loss for Hasselblad circular polarizer?

    Hello, my first post to the forum after many months of lurking and learning

    I recently purchased a circular polarizer (B50) from KEH for my Hasselblad 150mm f/4 Sonnar. I'm attempting to verify the stop loss so that I can compensate either on the lens or light meter. Would anyone have information on how to figure this out? Does the '-1' mean one stop of light is lost? Photo of the filter is below.


  2. #2

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    I'm thinking both the 2X and the -1 indicate one stop of light transmission loss. In my experience, polarizing filters reduce transmission by anywhere from 1.5 stops to 2 stops depending on manufacturer and field conditions. I've not used a Hasselblad polarizing filter, however. I would buy a roll of transparency film and do a simple field test on a bright, sunny day.

    Peter Gomena

  3. #3

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    The filter may be round, but it's not a circular polarizer.

    The numbers on the rim are what you are after: "-1" means one stop loss, "2x" means the same, expressed as a shutterspeed factor.
    Those figures are correct.

  4. #4

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    Thank you both for your replies. I was hoping the numbers would reflect those values but didn't want to assume. I suppose my assumption regarding 'circular' was that since the filter can be turned it's circular..

  5. #5
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    That's right this is a linear polarizer
    Ben

  6. #6

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    How could you guys tell it's a linear polariser (from appearance)?

  7. #7

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    We just know.


    Hasselblad never sold circular polarizers, because no Hasselblad camera needs one.

  8. #8
    JLP
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    To elaborate a little on Q.G.'s statement.
    Film cameras don't need a circular polarizer, only digital cameras need them so you are fine with this filter.
    _______________
    Jan Pedersen
    http://janlpedersen.com

  9. #9

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    That's not quite correct, Jan.
    Whether a camera needs a circular polarizer or not depends on how its metering systems (either exposure or auto focus, or both) gets the light it needs to do what it should do.
    If there are reflecting surfaces in the light path from lens to metering system, light polarized by a polarizer on the lens might (not necessarily - it depends) not reach the metering system. That, depending on how the filter is oriented, i.e. in what plane the light behind it is polarized.
    So film cameras too may need a circular polarizer.

  10. #10
    JLP
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    I stand corrected then.
    Will the mirror then not be a reflecting surface?
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