Lens filters were an important part of my equipment when I used film cameras. When shooting weddings and portraits I would have an entire bag full of Cokin filters, indispensable for obtaining the variety of photo effects in vogue at the time. Shooting black and white film meant packing red, orange, yellow and green colored filters to increase the impact of sky and foliage. Color film meant packing filters to color balance the light at the location. These filters were in addition to the polarizing and neutral density filters that were always at hand.

You will still find a polarizer, circular now instead of linear, and neutral density filters in my bag. The rest of those indispensable filters are buried in a box in the corner of the garage. Today, even basic photo editing software can duplicate the results of white balancing, colored and special effects filters, often with far better control. So far, though, software programmers haven’t been able to successfully replicate the way a polarizing filter can render an image.

Polarizers add a dimension to landscape images not obtainable by any other method, rendering skies brilliant blue and foliage a deeply saturated green. They will reduce or eliminate reflections on water, glass and other non-metallic surfaces while increasing contrast and saturation. Their effectiveness is best when they are at a 90° angle to the sun, decreasing as the sun moves to a position behind or in front of the camera.

With some scenes you may only want partial polarization, leaving a bit of reflection on an object. Polarizers are designed so they can be rotated when mounted on the camera's lens, allowing you to control the amount of polarization. Looking into the camera's viewfinder you will see the amount of reflections and saturation change as you rotate the polarizer.

There are two types of polarizing filters: linear and circular. Linear polarizers, once the standard, can confuse modern autofocus and metering systems and have been replaced by circular polarizers. As great of a tool as they are, polarizers are not for all conditions. Polarizers reduce the light entering the camera by as much as two stops. This is handy when you need a slow shutter speed under bright conditions; it is not so desirable when you are shooting birds in flight at dawn and need all the light you can get. Polarizers also give odd results on wide angle lenses as the amount of polarization will change visibly across the image to the other.

A polarizer is a must have item for me for many types of photography. Once you use one you will feel the same way.