In photography, the term shutter-speed refers to the amount of time that film or digital sensor inside of a camera is exposed to light while capturing an image. The shutter-speed, along with the lens aperture, combines to determine how much light reaches the film or sensor (the exposure).

The effect that the shutter-speed has on your photograph does not stop at the exposure. You can either freeze action, or increase motion blur depending on how you set the shutter speed.

Fast shutter speeds can be used to freeze motion, making everything appear to be frozen in time (left example, above). Longer shutter speeds can be used to create the impression of movement or motion in an image (right example, above). If the shutter speed is too long, your subject could appear blurred due to the subject's movement while the shutter is open.

In addition to blurring or freezing the subject of the photograph, the shutter speed can have an effect on the overall sharpness of the image. There is a limit to how slow of a shutter speed a person can hand hold without the aid of a tripod. When film was the medium of choice, the rule of thumb for the lowest hand-holdable shutter speed was typically:

f = focal length of the lens you are using

This would mean that if you were shooting with a 100mm lens, you would use a minimum shutter speed of approximately 1/100 s. The closest shutter speed to this would typically be 1/125 s.

With the move to digital, and the ever increasing resolving power of digital sensors, this rule of thumb has been updated to reflect that increase in resolving power. When using a digital SLR, we recommend that the slowest shutter speed you use when hand holding the camera is

f = focal length of the lens you are using
Please see the specifications for your camera to find the crop factor for your body

This would mean that if you were shooting with a 100mm lens with the EOS 7D, you would use a minimum shutter speed of 1/320 s.

Creative uses of shutter speed in photography

You can use your choice of shutter speed to give your photograph the look and feel that you desire. Please see the list below for some suggestions:

• To freeze the action or moving subject:
  Use a fast shutter speed such as 1/4000 to 1/500 sec.
  
• To blur a running child or animal giving the impressions of fast movement:
  Use a medium shutter speed such as 1/250 to 1/30 sec. Follow the moving subject through the viewfinder and press the shutter button to take the picture. If you are using a telephoto lens, hold it as steady as possibly to prevent camera shake.
  
• How to blur a flowing river or water fountain:
  Use a slow shutter speed of 1/30 sec or slower. Use a tripod to prevent hand-held camera shake.