A PRESCRIPTION FOR BETTER PHOTOGRAPHS
In photography, the Sunny 16 rule (also known as the Sunny f/16 rule) is a method of estimating correct daylight exposures without a light meter. Apart from the obvious advantage of independence from a light meter, the Sunny 16 rule can also aid in achieving correct exposure of difficult subjects. As the rule is based on incident light, rather than reflected light as with most camera light meters, very bright or very dark subjects are compensated for. The rule serves as a mnemonic for the camera settings obtained on a sunny day using the exposure value (EV) system.
The basic rule is, “On a sunny day set aperture to f/16 and shutter speed to the [reciprocal of the] ISO film speed [or ISO setting] for a subject in direct sunlight.” For example:
On a sunny day and with ISO 100 film / setting in the camera, one sets the aperture to f/16 and the shutter speed to 1/100 or 1/125 second (on some cameras 1/125 second is the available setting nearest to 1/100 second).
On a sunny day with ISO 200 film / setting and aperture at f/16, set shutter speed to 1/200 or 1/250.
On a sunny day with ISO 400 film / setting and aperture at f/16, set shutter speed to 1/400 or 1/500.
As with other light readings, shutter speed can be changed as long as the f-number is altered to compensate, e.g. 1/250 second at f/11 gives equivalent exposure to 1/125 second at f/16.
An elaborated form of the Sunny 16 rule is to set shutter speed nearest to the reciprocal of the ISO film speed / setting and f-number according to this table:
|Aperture||Lighting Conditions||Shadow Detail|
|f/22||Snow/Sand||Dark with sharp edges|
|f/11||Slight Overcast||Soft around edges|
|f/5.6||Heavy Overcast||No shadows|
|f/4||Open Shade/Sunset||No shadows|
|Add One Stop||Backlighting||n/a|