20 OCTOBER 2026 · EXPOSURE · TECHNIQUE · METERING
The Sunny 16 Rule: Nail Exposure Without a Meter
In full sun, f/16 with a shutter speed of 1 over your ISO is a correct exposure. At ISO 100 that’s f/16 at 1/100s, which most cameras round to 1/125s, and it works out to EV 15 - the same number a light meter would hand you on a clear day. That one fact has been printed on film boxes for decades, and it still earns its place in a digital bag for a simple reason: it’s a reading that can’t be fooled by a white dress, a black suit or a bright sky behind your subject.
The point isn’t to throw your meter away. It’s to have a second opinion that costs nothing and lives in your head.
The full stop ladder
The rule only covers bright, direct sun. The rest of the table steps the aperture open one stop at a time as the light weakens, keeping the shutter at 1/ISO the whole way. The cue for each row is the shadows, not how bright the sky looks to your eye:
| Conditions | Shadows look like | Aperture (shutter at 1/ISO) |
|---|---|---|
| Snow or sand in sun | Dark, sharp edges | f/22 |
| Full sun | Distinct, crisp | f/16 |
| Slight overcast, haze | Soft around the edges | f/11 |
| Overcast | Barely visible | f/8 |
| Heavy overcast | None | f/5.6 |
| Open shade, sunset | None | f/4 |
Each row is exactly one stop from its neighbours, so the whole ladder spans six stops from snow to open shade. At ISO 100 and 1/125s, that’s roughly EV 16 down to EV 11. Some versions of the table put open shade at f/5.6 instead of f/4; treat that row as a range, because “shade” under a single tree and shade on the north side of a building are not the same amount of light.
One more adjustment worth memorising: if the sun is behind your subject, open up one extra stop. A backlit portrait in full sun is an f/11 row, not an f/16 one, because the side of the face you’re exposing for is in its own shadow.
f/16 is a starting point, not a setting you have to use
Nobody shoots a portrait at f/16 in full sun. The rule gives you an exposure, and from there you trade stops the way you would with any other reading. Open the aperture one stop, double the shutter speed, and the exposure doesn’t change:
- f/16 at 1/125s
- f/11 at 1/250s
- f/8 at 1/500s
- f/5.6 at 1/1000s
- f/4 at 1/2000s
- f/2.8 at 1/4000s
All six are the same amount of light at ISO 100. So a headshot at f/2.8 in bright sun needs 1/4000s, five stops faster than where you started. If your shutter tops out at 1/4000s, f/2 in full sun at ISO 100 is a stop over with nowhere left to go, which is exactly when an ND filter earns its place - the ND filter post counts those stops the same way.
Doing this in your head mid-shoot is where people slip a stop. The exposure calculator does the bookkeeping in third stops: enter f/16, 1/125s, ISO 100 as the metered exposure (it reads back EV 15), set the new aperture to f/2.8, and it solves for the shutter speed that holds the exposure. Or lock the shutter and let it solve for ISO instead. It runs in your browser; nothing is uploaded.
Using it as a cross-check
This is where the rule actually pays for itself on a working day. Your meter is reading reflected light and assumes everything averages out to a midtone. Sunny 16 describes the light falling on the scene, so it doesn’t care what colour the subject is wearing.
Say you’re shooting a bride outdoors at ISO 100 in clear sun, and your camera’s meter suggests f/16 at 1/500s. Sunny 16 says f/16 at 1/125s. That’s two stops apart, which is too big to be rounding. Something in the frame is fooling the meter, and a white dress filling half the frame is the usual suspect: the meter sees a lot of bright and darkens the whole exposure to drag that white back to grey. Shoot the meter’s number and the dress comes out a dingy grey and her face goes dark.
The reverse happens with a groom in a dark suit against dark foliage. The meter wants to brighten everything, and the suit’s black turns charcoal while the skin tones blow out.
A rough working rule:
- Meter and Sunny 16 within a third of a stop: trust the meter, it’s reading the light correctly.
- Within a stop: probably the conditions are between two rows of the ladder. Check the shadows and pick the row that matches.
- Two stops or more apart: the meter is reacting to the subject, not the light. Go with the rule, take a test frame and check the histogram.
When the gap is coming from what’s in frame, switching metering mode often fixes the cause rather than the symptom - the metering modes breakdown covers which mode gets fooled by what.
Where the rule stops working
Sunny 16 is a daylight rule. It assumes the sun is reasonably high in a clear sky, and it gets less reliable as the light gets more complicated:
- Low sun. In the hour around sunset the light drops fast and keeps dropping, which is why the bottom row of the ladder lumps sunset in with open shade. Use it to get in the right neighbourhood, then meter. The golden hour post covers planning a session around that changing light.
- Indoors. Window light, tungsten and a reception hall have nothing to do with the sun’s output, so the table doesn’t apply. Use a meter or known anchors instead: a bright interior sits around EV 7-8 at ISO 100, seven or eight stops below full sun.
- Moving subjects. The rule gives you an exposure, not a shutter speed that freezes anything. Pick your shutter speed for the motion first, then trade stops back to the aperture.
There’s one useful spin-off at night. The Looney 11 rule says a full moon high in a clear sky exposes at f/11 and 1/ISO. The moon’s surface is lit by the same sun, so f/11 is one stop more than Sunny 16 would give it, which keeps it reading bright instead of grey. Your meter usually gets the moon wrong, since it’s a small bright disc in a black frame, so this is one place where the rule beats the camera outright.
Learn three rows, not six
You don’t need the whole table in your head. Remember full sun at f/16, overcast at f/8, and open shade at f/4, all at 1/ISO, and you can interpolate the rest from the shadows. Check the meter against one of those three every time you walk into new light, and the frames where it was two stops off stop reaching your card. If you want more short field habits like this one, they’re the kind of thing the field-notes emails carry now and then.
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