Sunny 16 rule
Sunny 16 is an old rule of the thumb for photographers, used to determine the correct exposure before camera's had built in light meters and fully automatic exposure control. It may still come handy, for example if you are a Nikon DSLR photograher and owns old non-CPU lenses.
The rule simply says that in the summer, in bright sunny conditions with the sun on your back, you can often get a reasonable exposure by setting your camera to f/16 aperture and an exposure lenght of 1/ISO. In other words, if you are shooting at ISO 100, set your camera for f/16 with an exposure of 1/100th of a second. If you shoot at ISO 400, you set your camera to 1/400th of a second. Check it out - it works great!
If you buy a packet of Kodak Gold ISO 100 film, you may even find a reminder about the Sunny 16 rule on the flap!
As noted Sunny 16 only works with the sun on your back. Turn 180 degrees, use f/8. At 90 degrees you'll often find that f/11 works best. The table below outline some other typical lighting conditions, and what aperture you should use with ISO 100 film and a shutter speed equal to 1/100 second.
|Aperture||Lighting Conditions||Shadow Detail|
|f/11||Slight Overcast||Soft around edges|
|f/8||Mainly Overcast||Barely visible|
|f/4||Heavy Overcast, or Open Shade||No shadows|