By Rae A. Costa
Regardless of your preference to shoot with film or digital, there should be one piece of equipment you shouldn't be without - a polarizing filter. Think of a polarizer as a pair of sunglasses for your camera. A polarizer modifies the amount of polarized light reflecting from your subject. If you primarily shoot outdoors, a polarizer should be the first filter you buy.
To get an idea of how a polarizer works, let's talk basic physics. Light rays travel in electromagnetic radiation - or better yet as 'waves'. When these waves hit a non-metallic surface, such as a rock or body of water, some of the light reflects back into the air. When this happens, the colors of your subject aren't as eye-popping and your photo ends up with a washed out look.
The crystals in a polarizing filter absorb the reflecting light waves allowing diffused light to be transmitted. This allows for better viewing of the subject without reflections and the colors are more vibrant.
There are two types of polarizing filters - circular and linear. Circular polarizers are the most common, because they work best on cameras with an auto focus system. They can also be used with manual camera operations as well. A linear polarizer however, won't work with an AF system. Because of the way a linear polarizer distributes light entering the camera's lens, the metering system can't get an accurate reading to ensure proper focus and exposure. Thus, a linear polarizer is better suited for manual systems.
Using a polarizer when shooting outdoor scenes can enhance your photos in a number of ways. Some of the benefits gained by using a polarizer are:
Eliminating reflections - Polarizers eliminate reflections on water surfaces, making water more see-through or transparent looking. What's underneath - rocks, fish, seaweed - becomes easier to see. Without a polarizer a beautiful ocean scene can become dominated by harsh reflections from the water's surface. Removing unwanted reflections can alter the mood of your scene and make the overall photo more pleasant.
Darkening blue skies - Polarizers deepen the color of blue sky. The maximum effect is achieved by shooting at right angles to the sun. This can be done by simply pointing your index finger at the sun and extending your thumb at a 90-degree angle to your finger. Line up you camera and take your shot.
Adding cloud contrast - Polarizers increase contrast in your photo by removing reflections. This allows clouds in an otherwise featureless sky to become more pronounced. This works well on partially overcast days. However, if the sky is completely cloudy, a polarizer won't work as well.
Intensify color saturation - Polarizers increase the color of just about any surface that's wet or shiny, such as leaves, rocks, flowers, and even feathers. Your subject will improve in color with just a turn of the polarizer.
The best way to determine the affect of your polarizer is to put it on your lens, look through the vewifinder, and turn the ring until you find the desired contrast. Take multiple shots of a scene with and without the polarizer and with it turned to varying degrees. Mark the picture with how it was taken and keep it on hand for reference. The only way to learn how your polarizer works is to take pictures.