Filter Factor Polarizers

Discussion in 'Exposure Discussion' started by hortense, Apr 25, 2006.

  1. hortense

    hortense Member

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    Estimates how many stops of increased exposure are required using a circular polarizer? I have no in-camera exposure meter.
     
  2. Dave Parker

    Dave Parker Inactive

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    Depending on the brand, I have seen anywhere from 1.75 to 3 stops, there should be a filter factor printed on the rim of the filter, what brand is it?

    Dave
     
  3. jeroldharter

    jeroldharter Member

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    I think that a filter factor of 2.5 (=1 1/3 stops) is typical.
     
  4. Christopher Walrath

    Christopher Walrath Member

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    Jared is close to on. but a circular polarizer increases/decreases in effect when rotated. This can swing a half a stop one way or the other. just something to bear in mind. Try using a hand held meter and meter the filter that way. Might get you closer than guessing.
     
  5. hortense

    hortense Member

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    Thanks Dave . The rim IS marked in 1-stop increment (plus/minus up to 2-stops). Didn’t’ look at it! Thanks for your help!
    MAC
     
  6. Ole

    Ole Moderator Staff Member Moderator

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    There is no difference in the filter facton between circular and linear polarisers.

    Checking the meter reading while rotating shows how much polarised light is being absorbed by the filter, so IMO it makes more sense to use a fixed factor. After all, you want the brigh reflections to be darker, don't you?

    A second way to use polarisers is just the opposite: to enhance reflections. When rotated so that the reflections are strongest that light goes straight through, the rest of the scene is still 2 1/3 stops darker.
     
  7. hortense

    hortense Member

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    Flash - Sounds like you've done this. I'll give it a try.
    Thanks,
    MAC
     
  8. hortense

    hortense Member

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    Ole - This sounds good. Thanks, MAC.

    .. and ALL you guys ... truly a knowledge tank.
     
  9. Soeren

    Soeren Member

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    Stupid question alert.
    I know the Polariser takes out reflections and darken the sky to a degree depending on angle to the sun etc. I also know that an incamera meter will give different exposures because of that but I though the filterfactor should be constant since those effects are desired and if using a handheld meter for incident metering it should result in the correct exposure of the ground.
    Am I totally wrong ?
    Cheers, Søren
     
  10. Ole

    Ole Moderator Staff Member Moderator

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    Søren, you're totally right. See my answer above.
     
  11. Soeren

    Soeren Member

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    Yeah you beat me to it. I'll better take a cource in fast writing :smile:
    Cheers, Søren
     
  12. Jim Jones

    Jim Jones Subscriber

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    You would be right if you were using reflected light metering.
     
  13. titrisol

    titrisol Member

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    PS Question... does any compnay still make warm polarizers?
     
  14. Dave Parker

    Dave Parker Inactive

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    Moose and Singh Ray as well as Hoya, Tiffen, there are still quite a few that make Warm Polarizers, they are quite popular in the nature photography and landscape arenas.

    Dave
     
  15. titrisol

    titrisol Member

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    thanks, mine got lost during the last move....
     
  16. Nick Zentena

    Nick Zentena Member

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