It’s pretty well known that a polarizer filter may deepen the color of blue skies, but the more subtle effects of a polarizer are often less known–and certainly worth exploring.
Polarizers limit the light that penetrates through them. As such, they help reduce contrast. Polarizers are like prison bars, where the light bouncing up and down through the bars passes through, but the light waves traveling horizontally do not. Of course, polarizing filters can be rotated, changing which directional light reaches a camera’s sensor and which does not.
When photographing shiny surfaces, such as water on rocks, the effects of even small rotations of a polarizer can be significant. As light bounces at different angles off various wet surfaces, the effects of diminished contrast varies significantly with even a 45 degree rotation.
The images above show rocks on a beach on Kelleys Island, Ohio, where Art Weber, the director of the National Center for Nature Photography, and I hold our annual Island Adventure photo workshop. Right after a partly cloudy sunrise field session, I turned my camera on this dark glacial erratic surrounded by lighter bedrock limestone. I framed the rocks with my Sigma 35mm f/1.4 lens pointed downward and shot away, rotating the filter 45 degrees for every frame. Thus, frame one and frame 9 are the same, with the images in between showing progressive variations.
A slight turn, as you can see, can make a noticeable difference. Contrast and color are affected. By reducing contrast on reflected surfaces, colors change. This is most noticeable when photographing leaves covered with water, but it can also be seen here as the warmer colors of the rock are no longer dominated—at certain angles—by the bluish sky reflected in the sheen of the rocks. The glossy surface “disappears” when the polarizer is cutting down bluish uni-directional light.
The animated GIF above shows the same shot with the filter rotated 45 degrees per shot. What you see here is what you should be carefully previewing in your viewfinder or LCD. Which position is best for what you want your picture to convey?
Polarization isn’t just about blue skies or wet surfaces. For the images below of wild chervil on Kelleys Island, you might expect the glossy surface of green leaves to be affected by the addition of a polarizing filter, but you might not anticipate the way the filter changes the appearance of the tree trunks. Parts of them darken or lighten as the filter is rotated.
My advice is to always carry a polarizing filter and experiment. Take a few frames without one and then take some with the filter on. Rotate your polarizer filter to see the varied effects.
Lastly, a few warnings. As anyone shooting Fuji Velvia could tell you, be careful not to polarize your sky too much. With this contrasty slide film, you can dial in so much polarization that skies may turn blue-black. Even today with digital imaging and wider exposure latitude, you still must be careful of producing too much of an effect. With wide angle lenses, just one portion of the sky—the part 90 degrees from the position of the sun—will appear darker.
Also, remember that a polarizer will allow you to see into the water, a good thing for tidal pool photography but often not-so-good for sunsets reflected on lakes and seas.
One last bit of advice. Buy a high quality polarizer that fits your largest filter size. Then buy inexpensive step down rings for all your other lenses. My 86mm Sigma Circular DG Polarizer Filter fits my large telephoto zooms. For portability, I also carry a 77mm Sigma Circular DG Polarizer Filter, which attaches directly or with step down rings to my other lenses.
For more information about the annual Sigma FitzSimmons Photography Island Adventure Photo Workshop, from which the images in this feature are drawn, visit the Workshops section of www.fitzsimmonsphotography.com.