In this week's podcast, I talk about the value of a polarizing filter for reducing reflection and deepening colors, especially in the sky. But the "world's handiest lens accessory" can also double as a neutral density filter.
Most circular polarizers have two f/stops of density. That means if the normal exposure is 1/15 at f/8, the with the polarizer attached, it will be 1/15 at f/4. Sometimes this works against you putting your shot in the clutches of camera shake. But there's one instance when a polarizer is invaluable -- when you want a long exposure, such as capturing water scenes.
This shot of Burney Falls in Northern California was recorded with a 4-second exposure. Because the lighting was good that day, I had a hard time getting an exposure long enough to produce the effect I wanted. By putting a polarizer over the lens, I was able to reduce the shutter speed and get that dreamy look I was hoping for.