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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 is a device used to measure the amount of light. In photography, a light meter (more correctly an exposure meter) is used to determine the proper exposure (photography), exposure for a photograph. The meter will include either a Di ...
. 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, or memory device, is any learning technique that aids information retention or retrieval (remembering) in the human memory for better understanding. Mnemonics make use of elaborative encoding, retrieval cues, and image ...
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 have the same EV (for any fixed scene luminance). Exposure value is ...
(EV) system. The basic rule is, "On a sunny day set
aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An ...
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 is open) when taking a photograph. The amount of light that rea ...
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. A closely related ISO system is used to describe the relation ...
r ISO settingfor a subject in direct sunlight."


Using the rule

The basic rule is, "On a sunny day set
aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An ...
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 is open) when taking a photograph. The amount of light that rea ...
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. A closely related ISO system is used to describe the relation ...
r ISO settingfor 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 and the shutter speed (i.e. exposure time) to or seconds (on some cameras second is the available setting nearest to second). * On a sunny day with ISO 200 film / setting and aperture at , set shutter speed to or . * On a sunny day with ISO 400 film / setting and aperture at , set shutter speed to or . As with other light readings, shutter speed can be changed as long as the f-number is altered to compensate, e.g. second at gives equivalent exposure to second at . More in general, the adjustment is done such that for each stop in aperture increase (i.e., decreasing the f-number), the exposure time has to be halved, and vice versa. This follows the more general rule derived from the mathematical relationship between aperture and exposure time—within reasonable ranges, 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 a positive real number that, when multiplied by itself, equals the number 2. It may be written in mathematics as \sqrt or 2^, and is an algebraic number. Technically, it should be called the princi ...
, thus the above rule.


Alternative rule

An elaborated form of the sunny 16 rule is to set shutter speed nearest to the reciprocal of the ISO
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. A closely related ISO system is used to describe the relation ...
/ setting and
f-number In optics, the f-number of an optical system such as a camera lens is the ratio of the system's focal length to the diameter of the entrance pupil ("clear aperture").Smith, Warren ''Modern Optical Engineering'', 4th Ed., 2007 McGraw-Hill Pro ...
according to this table: :


See also

* Looney 11 rule


References

{{Reflist


External links


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