Time

Big Thompson River
Rocky Mountain National Park
Photograph by Tom Atwood

Most snapshots are like gunshots - lasting a fraction of a second. Every photograph captures visually a certain amount of time, usually brief but not always. This picture of the Big Thompson River in Colorado is a 20-second exposure, blurring the water as it rushes over the rocks. A photograph like this is difficult during the day, when it is usually too bright for long exposures. But, by closing up the iris (or aperture) of the lens, and waiting until dusk, it's possible. Just bring a tripod, and avoid slipping on the rocks, made smooth by the river over the years. Shutter: 20 seconds; Aperture: f/9.0; ISO: 100; Focal length: 18 mm.