Editing Sunny 16 rule

{{Short description|Method of estimating exposure in photography}}
{{For|the EP by Ben Folds|Sunny 16 (EP)}}
[[File:A. W. Jones Heritage Center, St, Simons, GA, US.jpg|right|thumb|Sunlit subject shot on a digital camera set to ISO 100, exposed at f/8 at 1/400 second which is the same [[exposure value]] as f/16 for 1/100 second, the recommended "sunny 16" exposure]]
In photography, the '''sunny 16 rule''' (also known as the '''sunny {{f/|16}} rule''') is a method of estimating correct daylight [[exposure (photography)|exposures]] without a [[light meter]]. 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]] for the camera settings obtained on a sunny day using the [[exposure value]] (EV) system.

==Using the rule==
The basic rule is, "On a sunny day set [[aperture]] to {{f/|16|link=yes}} and [[shutter speed]] to the [reciprocal of the] ISO [[film speed]] [or ISO setting] for a subject in direct sunlight."<ref name="suess">{{cite book | title = Mastering Black-and-White Photography | author = Bernhard J. Suess | publisher = Allworth Communications | year = 2003 | isbn = 1-58115-306-6 | url = https://books.google.com/books?id=7LaRPNINH_YC&dq=%22sunny+16+rule%22&pg=PT112 }}</ref> In simplest terms, bright sun = f:16 @ 1/[[Film speed|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 {{f/|16}} and the shutter speed (i.e. exposure time) to {{sfrac|1|100}} or {{sfrac|1|125}}<ref>{{cite book|last1=Shaw|first1=John|title=John Shaws's Nature Photography Field Guide|date=2000|publisher=Amphoto Bookds|isbn=0-8174-4059-3|page=16}}</ref> seconds (on some cameras {{sfrac|1|125}} second is the closest available setting to {{sfrac|1|100}} second).
* On a sunny day at ISO 200 and aperture at {{f/|16}}, set shutter speed to {{sfrac|1|200}} or {{sfrac|1|250}}.
* On a sunny day at ISO 400 and aperture at {{f/|16}}, set shutter speed to {{sfrac|1|400}} or {{sfrac|1|500}}.

Shutter speeds can be changed as long as the f-number is adjusted accordingly, e.g. {{sfrac|1|250}} second at {{f/|11}} gives equivalent exposure to {{sfrac|1|125}} second at {{f/|16}}. Exposure adjustments are done in a manner that retains the [[Exposure value|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 {{sfrac|1|''c''<sup>2</sup>}} and vice versa. A change in the aperture of 1 stop always corresponds to a factor close to the [[square root of 2]], 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 [[film speed]] and [[f-number]] according to a generalized exposure table, as:<ref>{{cite book
| title = Digital Photography Outdoors: A Field Guide for Travel and Adventure Photographers
| author = James Martin
| publisher = The Mountaineers Books
| year = 2004
| isbn = 978-0-89886-974-3
| url = https://books.google.com/books?id=XMd7CsUws6sC&dq=Slight+Overcast+16+Soft+around+edges&pg=PA70
}}</ref><ref>{{cite book
| title = Lighting Photo Workshop
| author = Chris Bucher
| publisher = John Wiley and Sons
| year = 2007
| isbn = 978-0-470-11433-9
| page = 58
| url = https://books.google.com/books?id=o6QUAI_WYZsC&dq=Slight+Overcast++f/11+%22Soft+around+edges%22&pg=PA59
}}</ref>
[[File:Tessina with exposure guide plate.JPG|thumb|right|Tessina with exposure guide plate from the 1960s. At that time, DIN 21 was equivalent to ASA 80. After 1983, DIN 21 was ASA 100.<ref>Ilford Manual of Photography  p. 415, 1981</ref> On this guide plate, DIN 21 uses f/16 and 1/125, consistent with Sunny 16.]]
:{| class="wikitable"
! [[f-number|Aperture]]
! Lighting conditions
! Shadow detail
|-
| {{f/}}22
| Snow/sand
| Dark with sharp edges
|-
| {{f/}}16
| Sunny
| Distinct
|-
| {{f/}}11
| Slight overcast
| Soft around edges
|-
| {{f/}}8
| Overcast
| Barely visible
|-
| {{f/}}5.6
| Heavy overcast
| No shadows
|-
| {{f/}}4
| Open shade/sunset
| No shadows
|-
| Add one stop
| Backlighting
| n/a
|}

== See also ==
*[[Looney 11 rule]]

==References==

{{Reflist}}

== External links ==
* [http://guidetofilmphotography.com/sunny-16-exposure.html Guide to Photography] Sunny 16 and film exposure guide.

[[Category:Photographic techniques]]
[[Category:Rules of thumb]]