Time lapse photography is, in principle, the process of photographing a slow-moving subject at chosen intervals, and replaying the captured images as a video presentation to speed up the action. In practice there are a number of difficulties to overcome.

It is not necessary to use a video camera to capture the time-lapse images. Any digital still camera can do the job. However, it is essential to have a tripod to keep the camera stationary, and some form of intervalometer - a device that fires a camera's shutter at predetermined intervals for as long as necessary.

The interval between exposures must be determined once the subject has been selected and the relevant rate of change is understood. A very slow-moving subject, such as a flower blooming, might be photographed at intervals of 30 minutes over a period of several days, but the movement of clouds across the sky would typically require one picture to be taken every 10 or 15 seconds.