A light meter feels like a given when you're working with a modern camera. You point, glance at your settings, and trust the camera to do the work for you.
But photography has been around for much longer than the digital sensor. Long before cameras took their own measurements, photographers knew perfectly well how to set their exposure. They looked at the sky.
Sunlight is, after all, remarkably predictable. This predictability forms the basis of the sunny-16 rule: a simple rule of thumb that used to even be printed on the packaging of film rolls.
What is the sunny-16 rule?
The rule is surprisingly simple.
On a clear, sunny day, you set your aperture to f/16. You then choose your shutter speed based on your ISO: approximately 1/ISO second.
If you shoot at ISO 100, you'll end up with a shutter speed of 1/100 second. In practice, you'll round this up to 1/125 second, the closest shutter speed on most cameras.
The same logic applies to other ISO values and apertures. This table gives you a handy overview for a sunny day:
| Aperture / ISO | 50 | 100 | 200 | 400 | 800 | 1600 | 3200 |
|---|---|---|---|---|---|---|---|
| f/2 | 1/4000 | – | – | – | – | – | – |
| f/2.8 | 1/2000 | 1/4000 | – | – | – | – | – |
| f/4 | 1/1000 | 1/2000 | 1/4000 | – | – | – | – |
| f/5.6 | 1/500 | 1/1000 | 1/2000 | 1/4000 | – | – | – |
| f/8 | 1/250 | 1/500 | 1/1000 | 1/2000 | 1/4000 | – | – |
| f/11 | 1/125 | 1/250 | 1/500 | 1/1000 | 1/2000 | 1/4000 | – |
| f/16 | 1/60 | 1/125 | 1/250 | 1/500 | 1/1000 | 1/2000 | 1/4000 |
| f/22 | 1/30 | 1/60 | 1/125 | 1/250 | 1/500 | 1/1000 | 1/2000 |
| f/32 | 1/15 | 1/30 | 1/60 | 1/125 | 1/250 | 1/500 | 1/1000 |
Why this works so well for street photography
Street photography changes with every step you take.
One moment you're in a brightly lit square. Five minutes later, you walk into a narrow alley where the light falls completely differently. If you then have to wait for your light meter to take a new reading, the moment is often gone.
Of course, you can shoot in aperture priority mode, or just use the P mode. That works. But you also give up control.
Your camera then decides what a good exposure is. Not you.
The sunny-16 rule isn't a law. It's a starting point. A way to react faster, because you already know roughly where your settings should be before you bring the camera to your eye.
How much you deviate from it depends on the light, your subject, and especially on what you want to do with the image.
Adjusting the rule for the weather
Not every day is bright blue and sunny. As soon as clouds appear, the light changes. And so your settings change with it.
This table helps you quickly estimate which aperture suits which type of light:
| Type of weather | Shadow | Aperture |
|---|---|---|
| Snow or sand | Dark with sharp edges | f/22 |
| Bright and sunny | Clearly defined | f/16 |
| Lightly cloudy | Softly fading edges | f/11 |
| Cloudy | Barely visible | f/8 |
| Heavily cloudy | No shadow | f/5.6 |
| Shadow or sunset | No shadow | f/4 |
On a lightly cloudy day, you'd go from f/16 to f/11, for example. If you're working at ISO 100, you'd end up with f/11 and 1/125 second.
Don't see this as a calculation you need to memorise perfectly. See it as practice.
The more you work with it, the faster you'll learn to estimate which settings are logical for a given situation. At some point, you'll be able to set up your camera before the image even appears.
And that's exactly what street photography is all about.
Not looking first, then measuring, then setting, and only then photographing. But thinking ahead. Anticipating. Being ready before the moment happens.
Even faster: combine with zone focus
The real speed gain comes when you combine the sunny-16 rule with zone focus.
If you already know which part of your image will be in focus, you only need to adjust your exposure while shooting. You no longer have to wait for autofocus. Or hesitate about your focus point. And just react.
This table shows which aperture fits different combinations of shutter speed and ISO:
| Shutter speed / ISO | 50 | 100 | 200 | 400 | 800 | 1600 | 3200 |
|---|---|---|---|---|---|---|---|
| 1/4000 | f/2 | f/2.8 | f/4 | f/5.6 | f/8 | f/11 | f/16 |
| 1/2000 | f/2.8 | f/4 | f/5.6 | f/8 | f/11 | f/16 | f/22 |
| 1/1000 | f/4 | f/5.6 | f/8 | f/11 | f/16 | f/22 | f/32 |
| 1/500 | f/5.6 | f/8 | f/11 | f/16 | f/22 | f/32 | f/64 |
| 1/250 | f/8 | f/11 | f/16 | f/22 | f/32 | f/64 | f/90 |
| 1/125 | f/11 | f/16 | f/22 | f/32 | f/64 | f/90 | – |
| 1/60 | f/16 | f/22 | f/32 | f/64 | f/90 | – | – |
| 1/30 | f/22 | f/32 | f/64 | f/90 | – | – | – |
Working with a camera like the Fujifilm X-Pro series, which has a combined ISO and shutter speed dial on top? You can set these to auto and primarily control your exposure using the aperture ring on your lens.
This makes it quick and intuitive. One movement, and you adjust your exposure to the light.
Just be mindful of the focus ring right next to your aperture ring. Especially with zone focusing, you don't want to accidentally change your focus distance without realising it.
Finally
As a modern street photographer, you don't need to memorise the sunny-16 rule.
But if you want to work faster, maintain more control, and be less reliant on your light meter, it's a valuable skill.
Especially when combined with zone focusing, the sunny-16 rule helps you shoot faster, more alertly, and more freely.
You'll no longer look at your camera first. You'll look at the light.
And once you've got that down, you're a lot closer to what street photography is all about: seeing, reacting, and not letting the moment slip away.