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Jan 23 2009

Using a Polarizing Lens

Posted by jeff in Photography

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A lot of people believe that a polarizing filter is just for eliminating reflections in glass or shiny subjects or for making blue skies darker.  While it does do these things well, the best use for a polarizer in landscape work is to eliminate color casts.  See, the problem is that whether you are shooting in overcast or blue skies, the color from the sky is reflecting off of the surface of everything around you.  The polarizing filter allows you to block the wavelength of light that is reflecting while allowing the direct wavelengths to pass through.  This means that you get more color saturation and less color cast from reflective surfaces like leaves.  To get the maximum benefit from your filter, set up your shot and then rotate your filter while looking through the camera.  Keep rotating until the color cast goes away and all your left is great saturated colors.

This first image was taken without the polarizing filter.  You can see that even though I was shooting in direct sunlight, there was distinct blue color cast.

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By using a polarizer and turning it for maximum effect, the cast is gone and the colors are more saturated.

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Related posts:

  1. The Polarizing Filter – Not Just for Pretty Skies
  2. Photoshop CS5 Feature 2 – Lens Correction
  3. Photography in Broad Daylight
  4. Shifting Perspective with the Lens Correction Filter
  5. Quick Lens Correction with PTLens

This entry was posted on Friday, January 23rd, 2009 at 12:01 am and is filed under Photography. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

7 Responses to “Using a Polarizing Lens”
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  1. ThoSo says:
    January 23, 2009 at 3:09 am

    Hi,
    while your are absolutely correct on the effect a polarizing filter has, the physics are not complete right.
    Let me try a still simplified but more correct version of the physics involved.

    It is all about the polarization of the light, meaning the direction of the light waves. Without any filter, in principle all directions are can be found at all wavelengths (red to blue). Now, since light (especially blueish light) is “reflected” or better scattered at the sky, especially at lower angles of the sun we see a polarization effect on this light. A polarization filter is able to either let exactly one polarization direction through. So it can be used to suppress light originating from the scattering. Similar effect take place when light is reflected from e.g. glassy surfaces, hence a polarization filter can be used to remove the reflected light in similar conditions (depending on the angle of light and surface). Btw., the same principle is used in connection with LCD displays.
    Cheers, Thoso

    Reply
  2. Raven says:
    January 23, 2009 at 8:04 am

    Hi!

    While this is probably true (and the effect sure is), something is missing. Except for skylight and actual lights all light is reflected so the filter can’t block all “direct wavelengths”. If that was true everything except the sky would be pitch black.

    Am I wrong?

    Reply
  3. Mike Palmer says:
    January 23, 2009 at 10:16 am

    I thought you would have some shots from Old Town today, My girlfriend at the time, her parents house is about 4 blocks from it – great place for some people shots. safe travels home Jeff

    Reply
  4. Antonio says:
    January 23, 2009 at 6:09 pm

    Raven

    Maybe I can help to explain a bit more. The polarizer is always blocking light but it is most effective with scattered light – and its not that simple. When light is scattered off a reflecting medium (whether that is water, glass or particles in the atmosphere) it does so with what some scientists call a preferred direction. If you want to eliminate that scattered light then you need to rotate the polarizer so that it aligns with that preferred direction (and that is why polarizers come with the ability for circular adjustment independent of the screw thread). Light which comes to you with a different preferred direction, or no preferred direction at all (i.e. ‘normal’ light) will still get through (and this is why everything doesn’t go black – there’s always either a bit of ‘normal’ light or light with different preferred directions around).

    So what is that preferred direction? It depends on the direction that the light is coming from and then scattered to. So for the landscape photographer, say, the source of light is usually the Sun and you with your camera is the direction that the light is scattered to (with the scattering medium in the middle). Now the preferred direction will be in a direction which is 90 degrees from those two lines. For instance, if you are framing a picture of a lake then the light comes from above and is scattered to you from the lake surface. The preferred direction of that scattered light is parallel to the lake surface, and by rotating the polarizer to the correct angle you can cancel out that scattered light, which is usually the glare that you see (or specularity as some refer to it) e.g. from ripples on the lake surface. Look up at the sky and rotate the polarizer and you’ll see that different patches of the sky darken as you do. That’s because for the sky, those preferred directions rotate about the Sun. Shoot in the early morning or late evening (and looking to the North or South) then most of the sky will darken when you angle the polarizer appropriately as the sunlight is coming from predominantly one direction.

    Also, the polarizer is always blocking off light, but when that light is direct (i.e. it hasn’t been scattered off a surface) then there isn’t a preferred direction and it only serves to cut the light intensity down. I use this to good effect sometimes when I want to lengthen my exposure time.

    Gosh! I’m really sorry, that was long winded! I hope it was informative and not boring though….! ;-)

    Reply
  5. Antonio says:
    January 23, 2009 at 6:10 pm

    Double gosh! I forgot to say – nice post Jeff!

    Reply
  6. Doug Herrick says:
    January 24, 2009 at 11:27 pm

    All those explanations!!! Chances are, if you have tried a polarizing filter you’re probably still using it. I leave mine on 99% of the time, outdoors, HDR, indoors, with flash and without it, in the dark and in the noon day sun. Oh, I use a tripod 100% of the time.

    Reply
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