Polarizing filters

Discussion in 'Photography Beginners' Forum' started by xfloggingkylex, Mar 16, 2007.

  1. xfloggingkylex

    xfloggingkylex TPF Noob!

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    polarizing filters seem to come up in question a lot, especially in the beginners place because they are filters that seem to become part of everyones kit, and it is one of the few filters that cant be replicated by software. I want to make an ongoing thread that shows the impact of polarizers firsthand so that everyone can see what all the hype is about.

    For these shots I simply held the filter in front of me to get the effect I wanted and then hand held shot the picture. notice in the first picture that the filter obviously produces a slightly darker image. This is because of the filter itself being gray, requiring about a stop extra light to produce the same exposure as a bare lens (meaning it is a weak neutral density filter). For the second picture, I rotated the filter so it would polarize the light from my monitor. Here are my results:

    normal:
    [​IMG]

    polarized:
    [​IMG]

    I'll be adding more pictures to show changes in contrast as well as reflection reduction later. Anyone who has or would like to take pictures showing the effect, do so here!
     
  2. Riggaberto

    Riggaberto TPF Noob!

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    Oooo I'll contribute to this thread soon when I get my latest slides back. Maybe not soon actually, because I'll develop them when I can actually afford to :(

    But at any rate, I took a lot of photos of the same thing comparing polarization effects, with the focus on both saturation, and reflection elimination, I'm excited to see them and will post.
     
  3. ericande

    ericande TPF Noob!

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    The following photos of Mt. Rainier were taken back to back from a ferry with no changes or photoshop, just a twist of the filter:

    [​IMG]

    [​IMG]
     
  4. xfloggingkylex

    xfloggingkylex TPF Noob!

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    now THAT is an increase in saturation. The water is so blue.
     
  5. cosmonaut

    cosmonaut No longer a newbie, moving up!

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  6. xfloggingkylex

    xfloggingkylex TPF Noob!

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    as promised I have some reflection reduction pictures to show the effect of the polarizer. These pictures are without and with the polarization effect (rotating the filter to get the effect)

    These are all directly from the camera, a K10D using a 50mm 1.4 with a hoya HMC multi coated circular polarizing filter. No editing what so ever.

    without: notice the glare off of the glossy paint on my sink.
    [​IMG]

    with:
    [​IMG]

    without: Just a little glare on the glass here
    [​IMG]

    with:
    [​IMG]

    without: the glare on this granite slab is very obvious
    [​IMG]

    with: alot more pleasing to the eye
    [​IMG]

    without: the glare from the leaves is obvious
    [​IMG]

    with: this produces much greener leaves
    [​IMG]

    without: the slight reflection on the table is somewhat distracting
    [​IMG]

    with: now it is gone and the picture is clean
    [​IMG]

    I am wondering though, I cant seem to eliminate the strong glare that is seen from looking at glass as an angle that turns the glass into basically a mirror. Sometimes it tones it down, sometimes not, but it never completely goes away. Am I just not aiming the polarizer correctly? I am new with using this but I want to make sure it is working the way it is supposed to.
     
  7. cosmonaut

    cosmonaut No longer a newbie, moving up!

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    Nice experiment, I enjoyed it. I never would have thought of this. Nice work.
    Cosmo
     
  8. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    For the maximum reduction of reflection the light should be striking the subject at an angle of 30 degrees, and the camera must also be pointed at the subject at an angle of 30 degrees.

    Google "polarizer eliminate reflection", and similar keywords, for more than you probably ever wanted to know about how polarizing filters work.
     
  9. ashfordphoto

    ashfordphoto TPF Noob!

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    ok. so when is a BAD time to use a polarizer? night? :blushing:
     
  10. xfloggingkylex

    xfloggingkylex TPF Noob!

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    yes. anytime where the lighting is not good enough. The filter I have is a 1.3 stop reduction in light, and in a dark room when you screw on the filter things become black in the viewfinder. Also I can see it not being a good idea to use with quick moving action, because if you only have time to focus and compose the shot, you wont have time to turn the polarizers ring to get the effect you want and as a result you are loosing light for no reason.

    Still, with a tripod you could use a polarizer any time, as long as the long exposure doesnt have an effect that you dont want (maybe a person may walk in front of the camera during your exposure if you are taking a picture of a busy street, or the slight wind is blurring the tree's when you lose that extra stop of light).
     
  11. OmlessWanderer

    OmlessWanderer TPF Noob!

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    So I understand the hows and whys of a polarizer but I've always been curious what causes the adjustment with a ring polarizer? Mechanically speaking, what happens when you turn the ring that causes the level of polarization to increase or decrease? Is it really a gradient filter and when you turn the ring you move the gradient in to place? Does it adjust the distance to and from the outer element? What makes this tick?! :)

    Thanks...
     
  12. Garbz

    Garbz No longer a newbie, moving up!

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    A polariser lets light through which is only polarised in a certain angle. When light strikes something such as the atmosphere parts are reflected parts are passed through, and the light changes polarisation angle. Now depending on the surface and the angle of incidence and the source of the light this angle is pretty much calculatable to physicists who know more about it than I do.

    So if you change the angle of polarisation you go from letting through all light to light just at 90 degrees. It is interesting to note that the light coming out of a polariser is polarised at a constant angle. The reason in the first picture why the light is black is because LCDs have a polariser in front of them as part of how LCDs work. In the first picture the polariser is at the same angle as the screen's and the light loss is due to imperfections in material. In the second picture both polarisers are at 90degrees to each other. The end results is the first blocks all light not moving vertically, and the second all not moving horrizontally, and nothing gets through.

    That's how I understand it from a physics class I took years ago anyway.

    Just to really screw with your mind here's what happens when 3 polarisers are in. 1 at 0degrees, 1 at around 30, the other at 90. Now you'd think that the 0 and the 90 would block all light, so why can I see through the 30 :). Note it only happens when the 30 is the middle element.
    [​IMG]

    /EDIT: Forgot to mention, by far the most practical thing about pol filters is they cut through a lot of haze on a sunny day.
     

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