During my recent trip to Yellowstone National Park, one of the accessories I reached for most often was a neutral density filter. This filter blocks some of the light from reaching the sensor--which allows for slower shutter speeds. I like the affect that a longer exposure brings to many of the photographs that include water or clouds.

Fishing Hole For this image of the Fishing Hole at the West Thumb of Yellowstone Lake, I used a neutral density filter to reduce the exposure by eight stops. The shutter speed of 25 seconds helps smooth the water and give the photo an otherworldly look.

I use the Singh Ray Vari-ND filter. This variable filter allows me to dial in the intensity of the filter from two to eight stops. I simply set the ISO and aperture on my camera--and then rotate the Vari-ND filter until I achieve my preferred shutter speed! When using very wide angle lenses, vignetting is something to keep an eye on as the edges of the filter may enter the frame and darken the corners of the photo. The variable neutral density filter is expensive. But, you also need to consider that it replaces multiple filters in your bag.

As the story goes, years ago fishermen would catch fish in the lake and then dip them into the Fishing Hole to cook. The water inside the cone is boiling! The national park service no longer allows Fishing Hole to be used as a cooking device.