Movement in Long Exposures
Taking a quick photo, using either a flash or a fast lens with sufficient ambient light, is pretty simple. But what if the situation remands a longer exposure, on the order of seconds, minutes, or even hours?
Obviously, this is one of the cases when you definitely want to use a tripod and preferably either a self-timer or a remote trigger. (For exposures over 30 seconds, you'll probably have to use bulb mode on your camera, which keeps the shutter open until you trigger it again).
With a long exposure, moving objects will often become completely invisible, but light sources - be it the headlights of a car, a flashlight, or otherwise - will be captured in the photograph. In the picture at right, for example, the spinning fair ride creates an interesting effect. This particular shot was taken in 2/5 of a second, just slow enough to blur out most of the ride details while leaving a show of lights.