The Sunny f/16 Rule

By Mark Evans on December 12, 2008

Quite simply the Sunny f/16 Rule states that: On a bright sunny day, with camera aperture set to f/16, the shutter speed will be 1 over the ISO value. eg when using ISO 100 film, aperture set to f/16 the shutter speed will be 1/125 (closest to 100). So if you were using ISO 50 shutter speed would be 1/60, and when using ISO 200, shutter speed will be 1/250. You get the idea. I like this rule because from this information you can derive other combinations that give the same exposure eg (f/16, 1/125s), (f/8, 1/250s), (f/5.6, 1/500s) etc. I would say less and less people tend to use this rule due to cameras with auto exposure etc, but I find it useful to have a starting point so I can roughly calculate exposures myself – cameras sometimes get it wrong!