The Sunny 16 Rule: A Practical Exposure Guide
Use the Sunny 16 rule to estimate daylight exposure, then trade aperture, shutter speed, and ISO without changing total exposure.
Manual exposure
Sunny 16 is a daylight starting point, not a promise
In bright, direct sunlight, set the aperture to f/16 and choose a shutter speed close to the reciprocal of the ISO. At ISO 100, that means roughly 1/100 second; on cameras with traditional shutter steps, 1/125 second is the usual nearby setting.
f/16 · shutter ≈ 1 / ISO
Trade one stop for another
Aperture, shutter speed, and ISO are linked. Opening the aperture by one stop doubles the light reaching the sensor, so maintaining the same exposure requires a shutter speed that is one stop faster or an ISO that is one stop lower.
A practical weather starting chart
| Conditions | Starting aperture | At ISO 100 | What to watch |
|---|---|---|---|
| Bright sun, hard shadows | f/16 | 1/125 s | Bright highlights |
| Slight overcast | f/11 | 1/125 s | Softening shadows |
| Overcast | f/8 | 1/125 s | Subject contrast |
| Open shade | f/5.6 | 1/125 s | Reflected sky light |
These are conventional starting points, not universal meter readings. Snow, sand, haze, backlighting, latitude, and time of day can all move the correct exposure.
How to use Sunny 16 with a digital camera
- Choose a deliberate ISO. Start low in bright light unless you need a faster shutter speed.
- Set the baseline exposure. Use f/16 and the closest available reciprocal shutter speed.
- Trade settings for the creative goal. Open the aperture for shallow depth of field or raise shutter speed to freeze motion while preserving equivalent exposure.
- Check the histogram and highlight warning. Make a small correction when important highlights clip or shadows lose needed detail.