# Sunny 16 rule
The Sunny 16 rule is a rule of thumb in photography for setting exposure without a [light meter](https://www.edgepedia.org/light-meter): in bright, direct sunlight, set the aperture to f/16 and the shutter speed to the reciprocal of the ISO (film speed), so ISO 100 film is shot at f/16 and about 1/100 second.[1](https://www.dpreview.com/articles/3624260730/absolute-beginner-s-guide-to-film-photography-the-sunny-16-rule-or-how-to-expose-with-no-meter/) It dates from the film era, when photographers had to estimate exposure by eye, and it remains in use with film cameras that lack a working meter and as a sanity check on meter readings.[2](https://blog.skylum.com/sunny-16-rule-for-flawless-exposure-settings-2/) • [1](https://www.dpreview.com/articles/3624260730/absolute-beginner-s-guide-to-film-photography-the-sunny-16-rule-or-how-to-expose-with-no-meter/)
| Key fact | Detail |
|---|---|
| Basic rule | Bright direct sun: f/16 at a shutter speed equal to 1/ISO; ISO 100 gives roughly 1/100 second, ISO 400 gives 1/500 second on a traditional dial[1](https://www.dpreview.com/articles/3624260730/absolute-beginner-s-guide-to-film-photography-the-sunny-16-rule-or-how-to-expose-with-no-meter/) |
| Condition ladder (ISO 100 at 1/100 sec) | Snow or sand f/22; sunny f/16; some clouds f/11; overcast f/8; heavy overcast f/5.6; sunset f/4[1](https://www.dpreview.com/articles/3624260730/absolute-beginner-s-guide-to-film-photography-the-sunny-16-rule-or-how-to-expose-with-no-meter/) |
| Lighting scope | Frontlit subjects, from 2 hours after sunrise to 2 hours before sunset[3](https://pages.cs.wisc.edu/~bolo/photo/sunny16.html) |
| Metered value | Bright sun meters to EV 15 at ISO 100, about 1/3 stop less than the rule's nominal exposure[4](https://www.scantips.com/lights/sunny16.html) |
| Origin | Traced to the 1941 Kodak Exposure Guide, which standardized exposure values using calibrated photometers[5](https://frameandfocal.com/post-processing/photography-cheat-sheet-the-sunny-16-rule) |
| Main uses | Exposure on meterless film cameras; a reality check when a meter may be fooled; presetting exposure for candid shots[1](https://www.dpreview.com/articles/3624260730/absolute-beginner-s-guide-to-film-photography-the-sunny-16-rule-or-how-to-expose-with-no-meter/) • [3](https://pages.cs.wisc.edu/~bolo/photo/sunny16.html) |
## How the rule works
The rule rests on the fact that bright sun is a nearly constant light source, so a frontlit outdoor scene in direct sunlight always needs about the same exposure; haze and atmospheric conditions introduce the main variation.[4](https://www.scantips.com/lights/sunny16.html) Setting the aperture to f/16 and the shutter speed to the reciprocal of the ISO produces a usable exposure, even if not a perfect one. With 100 ASA film the nearest dial speeds are 1/90 or 1/125 second; with 400-speed film, f/16 at 1/500 second.[1](https://www.dpreview.com/articles/3624260730/absolute-beginner-s-guide-to-film-photography-the-sunny-16-rule-or-how-to-expose-with-no-meter/)
**Adjusting for conditions.** As light dims, the aperture opens one stop at a time: f/11 with some clouds, f/8 under overcast, f/5.6 under heavy overcast or in open shade, and f/4 at sunset. Very bright scenes such as snow or sand call for stopping down to f/22.[1](https://www.dpreview.com/articles/3624260730/absolute-beginner-s-guide-to-film-photography-the-sunny-16-rule-or-how-to-expose-with-no-meter/) • [3](https://pages.cs.wisc.edu/~bolo/photo/sunny16.html) Direction of light matters as well: for a close side-lit subject, open one stop (f/16 to f/11), and for a close backlit subject, open two stops (f/16 to f/8); closeups of backlit subjects use f/5.6.[3](https://pages.cs.wisc.edu/~bolo/photo/sunny16.html)
Because aperture and shutter speed are interchangeable in one-stop steps, the rule's exposure can be shifted for creative purposes. A sunny ISO 100 exposure of f/16 at 1/125 second can be opened three stops to f/5.6 with a three-stop faster shutter of 1/1000 second for shallower depth of field.[1](https://www.dpreview.com/articles/3624260730/absolute-beginner-s-guide-to-film-photography-the-sunny-16-rule-or-how-to-expose-with-no-meter/)
## Why it survives in the metered era
**Meters can be fooled.** Exposure meters are calibrated for middle gray, which matches most mixed scenes but fails on unusually light or dark subjects such as a snowy landscape or a dark building; the meter renders them as gray and recommends the wrong exposure.[1](https://www.dpreview.com/articles/3624260730/absolute-beginner-s-guide-to-film-photography-the-sunny-16-rule-or-how-to-expose-with-no-meter/) In one worked example, a jet-black car on ISO 200 film in sunny conditions draws a meter recommendation of f/8 at 1/250 second, two stops off the Sunny 16 value, a good indicator that the meter is wrong.[1](https://www.dpreview.com/articles/3624260730/absolute-beginner-s-guide-to-film-photography-the-sunny-16-rule-or-how-to-expose-with-no-meter/) Older film cameras are especially vulnerable because most models from the 1960s, 70s, and 80s use center-weighted meters that average the scene with emphasis on the middle, and some can be thrown off simply by turning the camera sideways.[1](https://www.dpreview.com/articles/3624260730/absolute-beginner-s-guide-to-film-photography-the-sunny-16-rule-or-how-to-expose-with-no-meter/)
The rule also helps with consistency: it fixes exposure from shot to shot instead of letting the camera re-guess with every framing change, and it lets a photographer preset settings for candid or time-constrained shots before raising the camera.[6](https://www.digitalcameraworld.com/tutorials/photography-cheat-sheet-the-sunny-16-rule) • [3](https://pages.cs.wisc.edu/~bolo/photo/sunny16.html)
## Accuracy and limits
The rule is approximate rather than exact. Metered bright sun at ISO 100 reads EV 15, equivalent to 1/125 second at f/16, about 1/3 stop less than the rule's nominal 1/100 second, and humidity can shift readings further.[4](https://www.scantips.com/lights/sunny16.html) Early or late in the day, or under a low winter sun, exposure may need to be increased slightly.[6](https://www.digitalcameraworld.com/tutorials/photography-cheat-sheet-the-sunny-16-rule) A field variant closes the whole ladder one stop, with bright sun at f/11 and a bright light with light background at f/16.[3](https://pages.cs.wisc.edu/~bolo/photo/sunny16.html)
The rule assumes daylight falling on a frontlit subject, so it does not cover backlighting, interiors, or artificial light, and mixed light sources break its assumption.[7](https://www.youtube.com/watch?v=M6qnv_6qykw) • [8](https://zonelightmeter.com/blog/sunny-16-rule/) Sand and snow reflect two to three times what a meter assumes, which is why those scenes sit a stop down the ladder at f/22.[8](https://zonelightmeter.com/blog/sunny-16-rule/) Negative film tolerates mild overexposure well, which made the rule forgiving in its original black-and-white context; exposure is more critical for slide film and for digital sensors.[4](https://www.scantips.com/lights/sunny16.html)
**Beyond Earth.** The rule even applies in orbit, with an adjustment: NASA astronaut Donald Pettit, who has served as a crew member aboard the [International Space Station](https://www.edgepedia.org/international-space-station), notes that in exo-atmospheric sunlight you stop down two more stops because the sun is a lot brighter without atmospheric attenuation, and that shadows on spacecraft structure are far starker because there is no atmosphere to scatter light into them.[9](https://time.com/3810759/donald-pettit-space-photography/)
## References
1. [The absolute beginner's guide to film photography: the 'Sunny 16' rule, DPReview (Aaron Gold, March 19, 2021)](https://www.dpreview.com/articles/3624260730/absolute-beginner-s-guide-to-film-photography-the-sunny-16-rule-or-how-to-expose-with-no-meter/)
2. [Sunny 16 Rule: Master Exposure Without a Light Meter, Skylum Blog](https://blog.skylum.com/sunny-16-rule-for-flawless-exposure-settings-2/)
3. [Sunny 16 Rule, pages.cs.wisc.edu](https://pages.cs.wisc.edu/~bolo/photo/sunny16.html)
4. [Sunny 16 Rule for exposure, scantips.com](https://www.scantips.com/lights/sunny16.html)
5. [The Sunny 16 Rule: Your No-Meter Exposure Cheat Sheet, Frame & Focal](https://frameandfocal.com/post-processing/photography-cheat-sheet-the-sunny-16-rule)
6. [Photography cheat sheet: the Sunny 16 Rule, Digital Camera World (Rod Lawton, April 22, 2022)](https://www.digitalcameraworld.com/tutorials/photography-cheat-sheet-the-sunny-16-rule)
7. [CORRECT EXPOSURE: The Rule of 16, YouTube (Giuseppe Tripodi, 2025)](https://www.youtube.com/watch?v=M6qnv_6qykw)
8. [The Sunny 16 Rule, Explained, Zone Light Meter](https://zonelightmeter.com/blog/sunny-16-rule/)
9. [A Master Class in Space Photography with NASA Astronaut Donald Pettit, TIME](https://time.com/3810759/donald-pettit-space-photography/)
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*Topic: Encyclopedia › Arts and culture › Visual arts and design › Photography techniques, genres, and history*
*Initially written Sep 17, 2026 · Reviewed: Oct 25, 2026 · Edited: Oct 15, 2026; Oct 25, 2026 · Last review: Oct 25, 2026*
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License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license