Learning how to use a Polarized Filter

Discussion in 'Photography Beginners' Forum' started by phkc070408, Oct 15, 2019.

  1. phkc070408

    phkc070408 TPF Noob!

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    Hi all:

    I have a Canon T5i and a Tamron B008 18-270 zoom lens. I'm going plane spotting in a few days but the observation deck is behind a glass wall. I bought a polarized filter but am having trouble figuring out how to use it. My concern is glare from the glass.

    While I'll be spotting during daylight, I wanted to practice tonight, but since its dark out, I'm trying in my dining room. We have a China Cabinet with polished wood and glass windows. I took four shots, rotating the filter 90° between each shot, but I can't tell the difference. I admit I may not be using the right environment for learning, but it was worth a shot.

    I do have a few specific questions though:

    1. How do I know from looking at the filter if it is on or off? There are no markings on the perimeter other than the manufacturers name and model number.
    2. If my filter is fully off, meaning minimal effect, how many degrees do I rotate it to get full effect? I'm assuming it's either 90º or 180º.
    3. What is the best way to test the filter? I was going to go out and sit in the car tomorrow behind the windshield and take some pictures looking out.

    Photo Forum - Polarized Filter - Google Drive

    Here are the pictures that I took tonight, for what it's worth. I uploaded them to my G-drive because they are too big to upload directly.

    Can someone please help me with this? Thanks!!


     
  2. Grandpa Ron

    Grandpa Ron No longer a newbie, moving up!

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    My polarizer seems to darken at about 90 degrees and it does not seem to block very much light. I have not used it very much, because I thought it would act like an adjustable neutral density filter but it does not.

    It is suppose to block glare. I was told glare is often vertically polarized, so by rotating the polarizer find the point at which you can reduce glare.

    I am interested it what others have found and how they uses theirs.
     
  3. wfooshee

    wfooshee No longer a newbie, moving up!

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    Use a polarizing filter outdoors to block glare. You'll see a dot on the rim of the filter, point that dot toward the sun. From that you should infer that you can't really use effectively it if you're shooting towards or away the sun. I really don't think it will help much indoors, although I've not tried anything like that. Reflections in the glass aren't the same thing as glare.
     
  4. petrochemist

    petrochemist TPF junkie!

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    The effectiveness of a polariser in reducing reflections is dependant on the angle of the reflecting surface. Even so the maximum effect should be clearly visible in your situation, simply rotating the filter should reduce & enhance the reflections with positions 180° apart having the same effect. There will be 2 positions that maximise reflections & 90° from these positions that minimise reflections.
    There's no great advantage to simply rotating 90° between shots as you could end up with 4 identical shots with fairly minimal effect in each. You need to look through the filter whilst rotating it through 90°-180°.

    In a situation like yours, photographing through glass that you can get close to, there is another option that's generally more effective than a polariser (it won't usually work with on camera flash). Have your lens close to the glass & arrange something to block any light hitting the glass in front of the lens. This can be a dark fabric behind you & held to the edges of the glass, or a rubber lens hood pressed directly to the glass...
    Sometimes just a hat held up to block the image of a light on the glass can be enough :)
     
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  5. tirediron

    tirediron Watch the Birdy! Staff Member Supporting Member

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    A polarizer is neither 'on' nor 'off' rather it is a graduated application, relative to the source of the light. In general, the effects will be most noticeable when: The lens is at 90 degrees to the light source; and the light source is lower on the horizon. Automobile glass can be challenging as a polarizer will enhance the adhesive between the layers. I suspect that the reason your sample images (which I can't access ATM)
     
  6. phkc070408

    phkc070408 TPF Noob!

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    I just for back from a test run. While it's extremely cloud here, I just went out to the park with an open field. While I know most photo experts know this already, I'll post my results in case anyone else needs to know.

    I placed a green straw on my dashboard and it's reflection was clearly visible in my windshield from NOT behind the camera. I turned my camera on and turned the filter so the only reference point, the brand and model number stamped on, were at the top. The reflection of the straw was perfectly visible in the camera.

    I turned the filter and it gradually faded until it was turned exactly 90º, at which point the reflection of the straw, and all other miscellaneous reflections had vanished. I then turned the filter to the 180º mark and all of the reflections gradually returned. The 270º mark was the equivalent of the 90º mark.

    What was interesting is the threads that mount the filter onto the lens must have been strategically placed so the filter is tight on the lens at the proper point for the filter to be giving the minimal effect when the markings are perfectly vertical.
     
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  7. tirediron

    tirediron Watch the Birdy! Staff Member Supporting Member

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    I think this is more likely to be simply a result of the circumstances.
     
  8. wfooshee

    wfooshee No longer a newbie, moving up!

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    But what about glare outside the car, which would be the subject of your shooting in the first place. You're trying to shoot through a window, and using a polarizer to reduce reflections from the window. It WILL have an effect on what you're looking at outside, and it may not be an effect you want. In the right orientation, a polarizer will darken the sky, and with a wide enough view, even give an inconsistent sky, part rather dark, part quite a light blue, depending on where the sun is.
     
  9. Original katomi

    Original katomi TPF Supporters Supporting Member

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    Also wide angle lenses have a problem as there is a variation of effect over wide angle
    Sometimes standing/shooting at an angle through the glass can minimise the effect of the glass nothing worse than seeing your own reflection on the glass when trying to shoot through it
     
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  10. petrochemist

    petrochemist TPF junkie!

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    Polarizers can be very useful once you understand them, and not just for reducing reflections.
    If you have 2 you can get a whole range of extra effects like this:
    [​IMG]stressed stencil by Mike Kanssen, on Flickr
     
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  11. zulu42

    zulu42 TPF Supporters Supporting Member

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    Sometimes it's hard to determine through the viewfinder where the CPL should be set. The markings on the filter itself have no relevance in setting the position because the angle of polarized light will be different from scene to scene. Leaving it set at one mark on the filter won't work for the next situation - or even if you decide to rotate the camera from landscape to portrait orientation.

    What I do is watch the meter:
    Frame your shot, adjust exposure settings so the meter is at center. rotate the filter through 360 degrees - while watching the meter. The meter's exposure indication will move higher and lower as the filter is rotated. When the meter is at it's highest indication, the filter has minimum effect. When the exposure indicator is at it's lowest during the rotation of the filter - this is when the filter is having maximum effect.
     
  12. Derrel

    Derrel Mr. Rain Cloud

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    Your 4 sample photos look like they are affected by an on camera flash causing bright Reflections on polished wood. I do not think that in this case any si
    setting on the polarizer would make much of a difference. I'm pretty sure that you would have much better results if you were to try using the polarizer to remove Reflections on a river or creek or lake surface, rather than trying to remove the highlights caused by a direct Flash on wood, with the light source being located directly on the lens axis. I'm pretty confident that you will have much better luck Outdoors. Keep in mind that a polarizer can reduce glare on such things as leaves, and particularly on the suface of bodies of water... in fact a polarizer can remove the diffuse highlight that our mind and eyed associate with the surface of creeks and ponds and lakes, and sometimes a polarizer can actually make a photo look worse than using no polarizer.
     

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