Guide · Updated
The sunny 16 rule sets an exposure without a light meter. On a clear, sunny day, set the aperture to f/16 and the shutter speed to 1 over the film speed: ISO 100 gives 1/100 s, ISO 400 gives 1/400 s. For each step down in light, open the aperture one stop: f/11 in slight overcast, f/8 in overcast, f/5.6 in heavy overcast, f/4 in open shade. Pick the ISO and the light above to get the settings and every other aperture and shutter speed that exposes the same.
01 · The chart
Sunny 16 chart: the aperture for each light
The shutter speed is always 1 over the ISO, to the nearest marked speed. Only the aperture changes with the light, and the shadows tell you which row you are in.
| Light | Shadows | Aperture | EV100* |
|---|---|---|---|
| Snow or sand in sun | Dark, sharp edges | f/22 at 1/ISO | 15.6 |
| Sunny | Sharp, distinct | f/16 at 1/ISO | 14.6 |
| Slight overcast | Soft round the edges | f/11 at 1/ISO | 13.6 |
| Overcast | Barely visible | f/8 at 1/ISO | 12.6 |
| Heavy overcast | None | f/5.6 at 1/ISO | 11.6 |
| Open shade or sunset | None | f/4 at 1/ISO | 10.6 |
* Our arithmetic: log2(N² × 100) with the exact f-number (f/11 is 11.3), the scene’s exposure value at ISO 100. The rows and shadows are the rule’s usual table (Wikipedia, “Sunny 16 rule”). Kodak’s own tables give snow and sand f/16 for most films, a stop more light than f/22.
02 · Using it
How to use the sunny 16 rule
- Set the shutter speed to 1 over the ISO. ISO 400 film: 1/400 s. ISO 100: 1/100 s, or 1/125 s on a camera without a 1/100 setting. For a speed the camera lacks, take the nearest marked one: ISO 64 gives 1/60 s.
- Read the light by the shadows. Look at the edge of your own shadow on the ground. Sharp and dark is sunny. Soft round the edges is slight overcast. Barely there is overcast. No shadow at all is heavy overcast or open shade.
- Set the aperture for that light. f/16 in sun, f/11 in slight overcast, f/8 in overcast, f/5.6 in heavy overcast, f/4 in open shade or at sunset. Snow or sand in sun: f/22.
- Open up one stop for a backlit subject. With the sun behind your subject, give one stop more light: f/11 where the chart says f/16, or a shutter twice as slow.
- Trade aperture for shutter speed if you need to. Each stop you open the aperture, make the shutter twice as fast. f/16 at 1/125 s is the same exposure as f/11 at 1/250 s, f/8 at 1/500 s and f/5.6 at 1/1000 s. Open up for shallower focus or a faster shutter, close down for more depth.
03 · Why
Why sunny 16 works
A scene in full sun is lit by nearly the same amount of light from one clear day to the next, as long as the sun is well up. So the exposure depends on the film speed and the light, not on what you point at. Kodak and Fujifilm print the same kind of table in their film data sheets, for the hours between two hours after sunrise and two hours before sunset. The rule is that table in one sentence.
Exposure value (EV) puts aperture and shutter speed on one scale. One EV is one stop. Two settings with the same EV expose the same.
- The formula
- EV = log2(N² / t), for f-number N and exposure time t in seconds. f/16 at 1/100 s: log2(256 × 100) = 14.6.
- EV100
- The same scene’s EV at ISO 100: sunny 16 is 14.6, or 15.0 with 1/125 s. At another ISO the settings’ EV is EV100 + log2(ISO / 100), so ISO 400 at f/16 and 1/400 s is EV 16.6. The calculator shows both.
- One row down
- Half the light. The chart goes from f/16 to f/4 in four steps: sunny to open shade is 4 stops, 16 times less light (our arithmetic).
04 · Limits
When sunny 16 fails
The chart assumes a front-lit subject in the middle of the day. Here is where it drifts, and the fix.
- Backlight
- The chart is for a subject lit from the front. With the sun behind it, the side facing you is in shade and the rule underexposes it. Wikipedia’s table says add one stop; Fujifilm’s Velvia 100 sheet says backlit subjects may need a one-stop adjustment; Kodak’s Portra 400 and Ektar 100 tables say f/5.6 for a backlit close-up in sun, two stops more than f/11.
- Sidelight
- The lit side is exposed as the rule says; the side in shadow comes out darker. Decide which side the picture is about. On negative film, many photographers open up half a stop to a stop to keep the shadow side. On slide film that costs the lit side its highlights (a common practice, not a datasheet figure).
- Early and late sun
- Kodak and Fujifilm both limit their sunlight tables to the time from two hours after sunrise to two hours before sunset. Outside those hours the sun is low and the light is weaker than the chart assumes: open up, or meter.
- Winter and high latitudes
- Fujifilm’s Velvia 100 sheet asks for a lens opening half a stop smaller in summer and half a stop larger in winter, except for snow scenes. Far from the equator the winter sun stays low all day.
- Deep shade and indoors
- The chart’s last row is the open shade Kodak describes as a “subject shaded from the sun but lighted by a large area of sky”. Under dense trees, in a doorway or indoors there is far less light than f/4 at 1/ISO assumes. Use a meter.
05 · Films
How much a miss costs, by film
Sunny 16 is good to a stop in plain sun. What a stop does to the picture depends on the film.
| Film | What the maker says | For sunny 16 |
|---|---|---|
| Color negative | Kodak’s Gold 200 sheet: “wide exposure latitude—from two stops underexposure to three stops overexposure”. The Portra 400 and Ektar 100 sheets state no latitude figure. Portra 400’s published curve, as Clack reads it, runs straight to at least 6.5 stops over the reference exposure. | The most forgiving: a stop either way is inside Gold 200’s range. Kodak’s own daylight tables for Portra 400 and Ektar 100 put bright sun at f/11, about three-quarters of a stop more light than the chart (our arithmetic). Miss on the side of more light. |
| Black and white negative | Kodak’s Tri-X sheet: “wide exposure latitude”, “rich tonality maintained with overexposure and underexposure”. One stop under with normal development costs a slight loss in shadow detail. Its table puts bright sun at f/16 and snow at f/22, the chart’s own. | Forgiving, and Kodak’s table agrees with the chart to a third of a stop (our arithmetic). |
| Slide (reversal) | Fujifilm’s Velvia 100 sheet gives no latitude figure. Half a stop either way is what photographers quote; it is not Fujifilm’s number. In Clack’s model of Velvia 100, built from Fujifilm’s curves, 3 stops under is black and 2 over nearly white (our model). | The least forgiving: there is no print stage to fix a miss. Kodak’s Kodachrome 64 and 200 tables and Fujifilm’s Velvia 100 table all land within a third of a stop of the chart (our arithmetic), so the rule suits slides when the light is plain. Bracket when it is not. |
06 · Phones
Sunny 16 on a phone
A phone lens has one aperture, so the rule shrinks to two settings: ISO and shutter speed. Tick “Fixed aperture” in the calculator, enter your phone’s f-number and read the shutter speed. The tested phone for Clack, a CMF Phone 2 Pro, has a fixed f/1.88 lens.
| Light | Exact, f/1.9 at ISO 100 | Nearest marked |
|---|---|---|
| Sunny | 1/7,091 s | 1/6400 |
| Overcast | 1/1,773 s | 1/1600 |
| Open shade or sunset | 1/443 s | 1/400 |
Our arithmetic, EV = log2(N² / t) with N = 1.9.
In full sun that is a very fast shutter. Whether your phone can set it depends on the phone: a camera whose fastest shutter is slower overexposes by the difference, and one whose lowest ISO is above 100 needs a faster speed still (ISO 200 needs a shutter twice as fast). Most of the time the phone’s own meter does this for you. The rule is for knowing what to expect, and for setting a manual exposure when the meter is fooled by a bright sky or a dark wall.
07 · Clack
Sunny 16 in Clack
Clack is a film camera app for Android and iPhone. It meters for you, and when you want the exposure yourself it has the controls sunny 16 needs.
- Shutter speed and ISO
- Set by hand in thirds of a stop, the same scale as the calculator. A sunny-16 exposure on a phone is the shutter speed from the fixed-aperture readout and the lowest ISO you can set.
- Exposure compensation
- −2 to +2 stops on the metered exposure, where the phone’s camera allows it. +1 is the backlit subject’s extra stop. AE lock holds the meter’s choice where the phone supports it.
- What your phone allows
- The dials span the sensor’s own ISO and shutter range, so what you can set depends on the phone. The manual controls appear only where the phone’s camera can be set by hand. The aperture is the lens’s own; Clack does not change it.
Android · iPhoneComing soon to Google Play and the App Store. More about Clack
Questions
- What is the sunny 16 rule?
- A way to expose a photo without a light meter. On a clear sunny day set the aperture to f/16 and the shutter speed to 1 over the ISO: ISO 400 gives f/16 at 1/400 s. In weaker light open the aperture a stop for each step: f/11 in slight overcast, f/8 overcast, f/5.6 heavy overcast, f/4 in open shade.
- What is sunny 16 at ISO 100?
- f/16 at 1/100 s. On a camera with no 1/100 setting use 1/125 s, which is about a third of a stop less light. The same exposure comes from f/11 at 1/200 s, f/8 at 1/400 s or f/5.6 at 1/800 s.
- What aperture do I use on an overcast day?
- f/8, with the shutter speed still at 1 over the ISO. Slight overcast with soft shadows is f/11; heavy overcast with no shadows is f/5.6; open shade or sunset is f/4.
- What EV is the sunny 16 rule?
- About EV 14.6 at ISO 100 (log2 of 16² × 100, our arithmetic), often rounded to EV 15. With 1/125 s instead of 1/100 s it is EV 15.0. Each row of the chart down is one EV lower.
- Is it f/16 or f/22 for snow?
- The usual chart says f/22 for snow or sand in sun. Kodak’s Portra 400, Ektar 100 and Kodachrome 64 tables say f/16 for bright sun on light sand or snow, one stop more light; Kodak’s Tri-X 400 table says f/22.
- How accurate is sunny 16?
- Close for a front-lit subject in plain sun, and not a replacement for a meter in tricky light. Kodak’s and Fujifilm’s own daylight tables land within a third of a stop of it for Kodachrome, Velvia 100 and Tri-X 400, and ask for about three-quarters of a stop more light for Portra 400 and Ektar 100 (our arithmetic).
- Does sunny 16 work on a phone?
- The arithmetic does, but a phone lens has a fixed aperture, so you only choose ISO and shutter speed. At ISO 100 in full sun, f/1.9 needs about 1/7,100 s, which is faster than many phone cameras can set. Use the fixed aperture option in the calculator for your phone’s f-number.
Sources
- Sunny 16 rule (Wikipedia)
- Kodak Professional Portra 400, E-4050
- Kodak Professional Ektar 100, E-4046
- Kodak Gold 200, E-7022
- Kodak Professional Tri-X 320 and 400, F-4017
- Kodak Kodachrome 25, 64 and 200 Professional, E-55 (1996)
- Fujichrome Velvia 100 Professional data sheet
Stop differences between a maker’s table and the chart are our arithmetic: log2(N² / t) of the printed pair against the chart’s f/16 at 1/ISO. The calculator runs in your browser; nothing is uploaded.