The Sunny 16 Rule: Does it Still Work?
If you don’t know the Sunny 16 rule, you’re missing one of the fastest ways to arrive at a correct exposure in full daylight—without metering, guessing, or chasing your histogram.
The rule is simple:
On a sunny day, set your shutter speed to the reciprocal of your ISO and choose f/16.
ISO 100 → 1/100 at f/16
ISO 200 → 1/200 at f/16
Any camera. Any lens. Same light.
What the Sunny 16 Rule Really Is
Sunny 16 isn’t a trick or a shortcut. It’s an exposure for a known light source.
The sun’s brightness is effectively constant for most of the day, and its distance from the Earth doesn’t meaningfully change. When brightness and distance stay the same, exposure stays the same. That’s why Sunny 16 works—and why it always has.
As long as your subject is lit by direct, unobstructed sunlight, Sunny 16 gives you a reliable starting exposure without touching a meter.
It’s like having an incident meter in your head.
Why It Still Works on Modern Cameras
Technology hasn’t changed the physics of light.
Digital sensors may record data differently than film, but the amount of light falling on a scene hasn’t changed. A correct exposure in sunlight is still a correct exposure in sunlight.
When tested in real-world conditions—even in challenging scenes like snow or high contrast—the Sunny 16 exposure lands exactly where it should. Highlights are preserved, midtones are correct, and any clipped shadows are the result of scene contrast, not exposure error.
That’s an important distinction.
Reciprocity: Making the Rule Flexible
Sunny 16 gives you the exposure. What you do with it is up to you.
Using the exposure triangle and the law of reciprocity, you can shift shutter speed and aperture however you like while keeping exposure constant.
For example:
If 1/100 at f/16 is correct, then
1/1600 at f/4 is also correct
Same exposure. Different depth of field. Different storytelling.
If you close the aperture one stop, you slow the shutter one stop. If you open the aperture two stops, you speed up the shutter two stops. The light recorded doesn’t change—only how you shape the image.
This is where Sunny 16 stops being a rule and starts being a teaching tool.
Why This Beats Metering in Sunlight
Camera meters measure reflected light, not the light falling on the subject. That means every change in subject tone—white dress, dark suit, snow, asphalt—forces the meter to rethink exposure.
But under a constant light source, the correct exposure does not change.
Once you know the exposure for that light, there’s no reason to keep re-metering. Sunny 16 lets you lock in exposure and shoot consistently instead of letting the camera guess differently on every frame.
Using matrix or evaluative metering alongside Sunny 16 defeats the purpose and adds unnecessary steps.
Sunny 16 and Auto Exposure
You can use Sunny 16 in automated modes if you understand exposure compensation—but that again misses the point.
Sunny 16 is about knowing the exposure, not asking the camera to find it.
Because camera meters only see reflected luminance, they cannot verify Sunny 16 on their own. To verify the rule, you either make an exposure using Sunny 16—or you measure the light falling on the scene with an incident meter.
A simple gray card in full sun can also serve as a check: fill the frame, set your ISO, choose a shutter speed of 1/ISO, and see where f/16 lands. Any deviation comes from technique, calibration, or lighting—not the rule itself.
When Not to Use Sunny 16
Sunny 16 applies only to subjects in direct sunlight.
If your subject is in shade, the rule will intentionally render that subject darker. That may be accurate—but it may not be what you want creatively.
In those cases, you expose for the subject, not the sunlight. You measure or judge the light in the shade and adjust accordingly.
Sunny 16 isn’t universal. It’s precise.
Why This Rule Still Matters
Sunny 16 teaches you that exposure isn’t mysterious.
It reinforces how light behaves, how the exposure triangle works, and why manual exposure gives you consistency and control. Once you internalize it, daylight stops being something you fight and starts being something you recognize instantly.
Photography rules do work—when you understand what they’re describing.
Go outside. Set it once. Trust it. Then adjust creatively. That’s where photography actually starts.