In photography, the sunny 16 rule (also known as the sunny rule) is a method of estimating correct daylight exposures without a

light meter A light meter (or illuminometer) is a device used to measure the amount of light. In photography, an exposure meter is a light meter coupled to either a Digital data, digital or analog calculator which displays the correct shutter speed and f-nu ...

. Apart from the 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 A mnemonic device ( ), memory trick or memory device is any learning technique that aids information retention or retrieval in the human memory, often by associating the information with something that is easier to remember. It makes use of e ...

for the camera settings obtained on a sunny day using the

exposure value In photography, exposure value (EV) is a number that represents a combination of a camera's shutter speed and f-number, such that all combinations that yield the same exposure (photography), exposure have the same EV (for any fixed scene luminanc ...

(EV) system.

Using the rule

The basic rule is, "On a sunny day set aperture to and

shutter speed In photography, shutter speed or exposure time is the length of time that the film or digital sensor inside the camera is exposed to light (that is, when the camera's shutter (photography), shutter is open) when taking a photograph. The am ...

to the eciprocal of theISO

film speed Film speed is the measure of a photographic film's sensitivity to light, determined by sensitometry and measured on various numerical scales, the most recent being the ISO system introduced in 1974. A closely related system, also known as IS ...

r ISO settingfor a subject in direct sunlight." In simplest terms, bright sun = f:16 @ 1/ film-speed-number (aperture and shutter speed, respectively). For example: * On a sunny day at ISO 100 ("100 speed film"), the aperture is set to and the shutter speed (i.e. exposure time) to or seconds (on some cameras second is the closest available setting to second). * On a sunny day at ISO 200 and aperture at , set shutter speed to or . * On a sunny day at ISO 400 and aperture at , set shutter speed to or . Shutter speeds can be changed as long as the f-number is adjusted accordingly, e.g. second at gives equivalent exposure to second at . Exposure adjustments are done in a manner that retains the EV. As the aperture is opened (f:11, f:5.6, f:4, etc.) the shutter-speed/exposure-time is reduced by a factor of approximately one-half (1/250, 1/500, 1/1000, etc.) This follows the mathematical relationship between aperture and shutter speed where exposure is inversely proportional to the square of the aperture ratio and proportional to exposure time; thus, to maintain a constant level of exposure, a change in aperture by a factor ''c'' requires a change in exposure time by a factor and vice versa. A change in the aperture of 1 stop always corresponds to a factor close to the

square root of 2 The square root of 2 (approximately 1.4142) is the positive real number that, when multiplied by itself or squared, equals the number 2. It may be written as \sqrt or 2^. It is an algebraic number, and therefore not a transcendental number. Te ...

, thus the above rule.

Alternative rule

The sunny 16 rule can be used in varying light by setting the shutter speed nearest to the ISO

and

f-number An f-number is a measure of the light-gathering ability of an optical system such as a camera lens. It is calculated by dividing the system's focal length by the diameter of the entrance pupil ("clear aperture").Smith, Warren ''Modern Optical ...

according to a generalized exposure table, as: Tessina with exposure guide plate

References

{{Reflist

External links

Guide to Photography
Sunny 16 and film exposure guide. Photographic techniques Rules of thumb

Using the rule

Alternative rule

See also

References

External links