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How to Use the Sunny 16 Rule (And Other Exposure Settings)

Last updated: January 18, 2024 - 7 min read
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In photography, various rules help improve your photography. But what is the purpose of the Sunny 16 rule? The Sunny 16 rule helps you estimate which camera settings to use for a balanced exposure.

As the name suggests, it’s for shooting outdoors on sunny days using an f/16 aperture. So you’ll learn more about the famous Sunny 16 rule in this article.

Accurate Light Measurement
Sekonic L-308X-U Flashmate Light Meter
Sekonic L-308X-U Flashmate Light Meter
Improve your knowledge of the Sunny 16 rule and other exposure settings with a versatile and accurate digital light meter. It measures ambient and electronic flash light readings.

Sunny 16 Rule in the Digital Era

In the past, the Sunny f/16 rule or 16 rule was a must-have in a film photographer’s bag of tricks. This photography rule acts as a metering system when you don’t have a light meter.

But now, built-in light meters are present in every device. It’s in everything from camera phones to pro-grade mirrorless cameras.

Nonetheless, the Sunny 16 rule can still serve you well in several ways:

  • It makes you work faster in Manual mode with your digital camera.
  • It makes it easier to experiment with film photography. For example, when shooting large format 6×6 film.
  • It’s a useful exercise to improve your ability to read the available light. With a light meter app on your smartphone, you can check the settings you would use against those suggested by the app.
A screenshot of a pocket light meter app for using the sunny 16 rule
I like to use the app Pocket Light Meter on my iPhone to practice my ability to read light. Here, I bet on the Sunny 16 and was right.

How Does the Sunny 16 Rule Work?

The Sunny 16 rule states that, on sunny days, at an aperture of f/16, your shutter speed is the inverse of your ISO value.

For instance, if you set your camera at an aperture of f/16 and ISO 100, your shutter speed should be 1/100 s. This is one of the easiest photography rules to remember.

And it is a great starting point because you will no doubt want to change your exposure settings based on the reflected light available.

A car park on an overcast day as an example of light conditions that match the prediction of the Sunny 16 rule.
This is a good example of light conditions that match the prediction of the Sunny f/16 Rule.

The Exposure Triangle

The Sunny 16 rule works on the so-called exposure triangle. Your image exposure combines the aperture, shutter speed, and ISO values.

The triangle assumes you can get the same exposure by changing those values. When the lighting conditions change, you can raise your ISO, shutter speed, or aperture to reach the correct exposure.

A diagram showing how the Exposure Triangle. Shutter Speed, Aperture and ISO work together to determine the image exposure.
Shutter Speed, aperture, and ISO determine the image exposure.

Say you’re using an aperture of f/16, a shutter speed of 1/400 s, and an ISO of 400. You get the same exposure with the following camera setting combinations:

  1. f/11 (+1 EV), ISO 400 (0 EV), and 1/800 s (-1 EV)
  2. f/16 (0 EV), ISO 800 (+1 EV), and 1/800 s (-1 EV)

The overexposure or underexposure appears in the brackets. (EV stands for Exposure Value) But not all cameras and lenses let you shoot at f/16 or narrower apertures.

For example, my Sony RX100 does not close more than f/11. And Micro Four Thirds cameras start to suffer from diffraction over f/8.

Similar Rules to the Sunny 16 Rule

It is not always sunny outside. Some days are pretty dark, and the sunny f/16 rule does not fit those conditions. For this reason, there are different rules depending on the weather.

The Sunny 16 chart below illustrates the conditions for which the different rules apply:

  • Sunny 16 Rule: This is when you photograph in an open field on a sunny day.
  • Slight Overcast 11 Rule: This is when the sky is variable.
  • Overcast 8 Rule: This is for cloudy weather, but not when it’s dark.
  • Heavy Overcast 5.6 Rule: This is for bad weather, maybe when it’s rainy.
  • Sunset 4 Rule: This is for typical sunset conditions.
  • Snowy 22 Rule: If the sun is shining over a snowy landscape, f/22 is the suggested aperture. You get a balanced exposure using a shutter speed that is the inverse of your ISO.

Snowboarder int the air above snowy mountains


The principles are the same as the Sunny 16. In overcast conditions, follow the Overcast 8 Rule. To achieve a shutter speed of 1/100 s, you should set your camera to f/8 and ISO 100.

Let’s go over a couple more examples. This classic light (pictured below) suits the Overcast 8 Rule better than the Sunny 16.

A red brick building on an overcast day, light that suits the Overcast-8 Rule better than the Sunny 16 rule.

And this is a typical situation (pictured below) for the Heavy Overcast 5.6 rule.

A green park on an overcast heavy day, suitable for using the overcast-5.6 rule.


Forget the Weather, Read the Shadows

Actual sky conditions can be misleading. So look at shadow “hardness” to estimate which rule best matches the light conditions.

The sky looks great and clear in the photo below. But some clouds are blocking the sun. And as you can see, there are no shadows on the ground.

In these conditions, the light meter of my Sony RX100 Mark II told me that a balanced exposure would be obtained at an aperture of f/11, a shutter speed of 1/100 s, and an ISO of 100.

This is the Slightly Overcast 11 Rule.

Photo of a train pulling into a railway station on a day with blue skies and clouds
The sky suggests the Sunny f/16 rule should apply. But because of passing clouds in front of the sun, the in-camera light meter will tell you that the Slightly Overcast f/11 rule works better.

With very soft shadows or no shadows at all, you want to use the Heavy Overcast 5.6 Rule.

The Sunny 16 works best with hard, deep shadows. Anything in-between is for Overcast 8 or Slightly Overcast 11.

Diptych showing the difference between using the sunny-16 rule with hard shadows, or the overcast-5.6 for no shadows
Applying these rules will make you fluent in reading light and shadow hardness.

Applying the Sunny 16 Rule in Real Life

These rules are not exact. Reality is not made of individual factors (sun, clouds, heavy clouds, etc.).

It is an ever-changing mix of factors, and no bulletproof rules exist. This is why knowing how to read the light is important, particularly for an outdoor photographer.

Let’s consider the image below.

Leafy trees casting shadows over a bench, defying the sunny-16 rule
This image will defy the Sunny 16 rule.

You can see very strong shadows on the ground. But the in-camera light meter tells me to have a shutter speed inverse to my ISO (i.e.,1/100 s).

Instead, I should use an aperture of f/5 and not f/16, as the hardness of the shadows would suggest.
Why? Because the scene is rather dark due to the strong foliage.

Compare it to the image brightness below, taken only a few minutes later and under the same kind of daylight.
A photo of industrial type buildings on a cloudy day This image of open ground follows the Sunny 16 rule. In general, open-ground images are much brighter than those taken under the canopy of trees.


Conclusion: How to Use the Sunny 16 Rule

Thanks to in-camera light meters, the modern digital photographer does not need to memorize these rules. But practicing with the Sunny 16 rule is a great exercise to learn to read the available light. You can use our Quick Capture cheat sheets to have all the top photography rules at your fingertips.

Start practicing right away! Look out the window. Is that weather to use the Sunny 16 rule or something else?

Accurate Light Measurement
Sekonic L-308X-U Flashmate Light Meter
Sekonic L-308X-U Flashmate Light Meter
Improve your knowledge of the Sunny 16 rule and other exposure settings with a versatile and accurate digital light meter. It measures ambient and electronic flash light readings.