Identification

• The sunny 16 rule establishes relative camera settings for photography using bright sunlight. The camera aperture is set at f/16. The shutter speed is determined by the ISO film speed being used. Most photographers use ISO 50, ISO 100 film or ISO 200 film when shooting in sunlight. The sunny 16 rule calls for the shutter speed to be approximately one over the film speed number. For ISO 50 film, the shutter speed would be about 1/50 of a second, for ISO 100 film about 1/100 and for ISO 200 film about 1/200. Since most cameras have shutter-speed settings for 1/60 of a second, 1/125 of a second and 1/250 of a second, they are used instead.
  
  

Time Frame

• Photographers can adjust the sunny 16 rule to use a different time frame for the shutter speed. This is often done if a faster shutter speed is needed to capture a fast moving subject or a slower shutter speed is desired to create a special effect. If the shutter speed is changed on a sunny day, the f-number must also change to strike the same photographic balance. A shutter speed increase of 1/125 to 1/250 is one step faster on most cameras. If this is done, the f-number must be decreased one step from f/16 to f/11.
  
  

Effects

• The sunny 16 rule can also be applied to different outdoor lighting situations. It is still called the sunny 16 rule but the day does not have to be sunny and the f-number does not have to be f/16. On a lightly overcast day where the shadows are soft around the edges, the f-number can be dropped to f/11 using the same shutter speed, depending on the ISO film speed. On a moderately overcast day where you can barely see shadows, drop the f-number to f/8. On extremely overcast days where there are no shadows at all, the f-number can be lowered to f/5.6. If you are photographing in the shade or at sunset, reduce the f-number to f/4.
  
  

Function

• The sunny 16 rule is often used to determine whether a light meter is working or broken. A photographer sets the f-number and shutter speed according to the sunny 16 rule and takes a photograph. He will then compare that picture to one taken using the readings of the light meter. If the light meter disagrees with the sunny 16 rule, chances are the light meter is wrong.
  
  

Expert Insight

• Professional photographers swear by the sunny 16 rule. It is a baseline standard of photography. The sunny 16 rule produces dynamic pictures in situations where it is impractical to get out a light meter and take measurements. Journalists, vacationers and nature photographers all use the sunny 16 rule with great success. It works so well because it is so simple. All you have to do is follow the numbers. The sunny 16 rule gives experienced photographers a feel for the right settings. After a while they can just look at the light and know what f-number and shutter speed is needed.