Long exposure photography
is a technique that requires a slow shutter speed
to capture light and movement.
When an image is taken including stationary and moving subjects (for example, a fixed street and moving cars or a camera within a car showing a fixed dash-board and moving scenery) using a slow shutter speed, interesting effects, such as light trails occur.
Long exposures are easiest to accomplish in low-light conditions, but can be done in brighter light using neutral density filters or specially designed cameras.
While light trails at night are the most widely recognised form of long exposure photography, the same technique can be used to create light-paintings where the subject is kept dark, but the photographer moves lights about the subject.
Water and long exposure
Long exposure particularly lends itself to blurring moving water (particularly effective for waterfalls or for the sea at dusk if any object is
standing in it).
A solargraph is a long-exposure photograph which shows the path taken by the sun across the sky. One example of this is a single six-month exposure taken by photographer Justin Quinnell, showing sun-trails over Clifton Suspension Bridge
between 19 December 2007 and 21 June 1008. Part of the Slow light: 6 months over Bristol
exhibition, Quinnell describes the piece as capturing "a period of time beyond what we can perceive with our own vision." This method of solargraphy uses a simple pinhole camera
securely fixed in a position which won't be disturbed.