About ND and Polarizer filters

Discussion in 'Exposure Discussion' started by Roberto Fernández, Mar 18, 2010.

  1. Roberto Fernández

    Roberto Fernández Member

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    Hello, I am from Uruguay, and I am new in this forum. I would like to know if somebody can explain if two polarizer filters can be used instead of Neutral Density filters to extend exposure time. Thank you:smile:
     
  2. Rudeofus

    Rudeofus Subscriber

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  3. Doremus Scudder

    Doremus Scudder Member

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    Rudeofus,

    Great reply: succinct and informative.

    At the risk of seeming wordy in contrast, I'll still comment...

    When using two polarizers stacked, you change the amount of light transmission by turning. The problem is, when compared to ND filters, that there is no standard filter factor. You must meter through the filters in the exact orientation you will be using them. This is no problem with TTL meters, but if you're using a handheld meter, you need to make sure the polarizers end up on the camera lens correctly. Use the dot or printing to make sure they are oriented correctly. Also, when metering make sure that no stray light gets into the meter or you may end up underexposing. This is no problem with spotmeters, but with wider angle reflected light meters and incident meters, it can be tricky.

    If you're shooting color, you may have to add some cc filters to your mix. These will have to be determined by testing, since different polarizers behave differently.

    Best,

    Doremus Scudder
    www.DoremusScudder.com
     
  4. Mainecoonmaniac

    Mainecoonmaniac Subscriber

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    You could make a variable ND filter with two polarizer filters stacked and changing the orientation of the filters to suit your density needs.
     
  5. Roberto Fernández

    Roberto Fernández Member

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    Polarizers instead of ND filters

    Hello Friends, thank you for your responses. I think that the problem with two polarizers is a degraded quality images due to so much glass... With ND filters this can be avoided, am I wright? Does anyone have some images taken with two polarizers? Thank you again:smile:
     
  6. Q.G.

    Q.G. Inactive

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    You are quite right. Using a ND filter would be the better option.

    Polarizers are polarizers too, and will have more effect than just making the entire image look a bit darker. You may not like that.
     
  7. Rudeofus

    Rudeofus Subscriber

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    Q.G., if you use a circular polarizer as the filter element closer to the subject, you should not have these problems. You have to hold it turned around, i.e. the side normally facing your lens should face the subject.
     
  8. Q.G.

    Q.G. Inactive

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    That would work, yes.