Flash duration

Cameras have various methods of blocking the light from reaching the film or CCD. When a picture is taken this barrier, known as a shutter, will open and allow light to reach the film or CCD. Most cameras have a way of controlling how long the shutter stays open and this duration is known as the shutter speed. More sophisticated cameras can adjust from several seconds to speeds as rapid as 1/10,000sec. Cameras with wider ranges are usually more versatile.Buying advice: Look for a camera that has speeds way below 1/30sec. The longer the speed the lower the light you will be able to take pictures in without having to use flash. As an indication, a speed of around one sec is required to take street lit scenes and a speed of over 30 seconds for moonlit shots. Buy a model with a B setting if you're considering taking extremely long exposures.