back to top

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

A- A+

Subscribe Below to Download the Article Immediately

You can also select your interests for free access to our premium training:

Your privacy is safe. I will never share your information.
Related course: Quick Capture Cheat Sheets

In photography, there are various rules that help improve your photography.

What is the purpose of the Sunny 16 rule? The Sunny f16 rule helps you estimate which camera settings to use for a balanced exposure. As the name suggests, it’s for shooting outdoors during sunny days.

In this article, you’ll learn more about the famous Sunny 16 Rule.

Sekonic L-308X-U Flashmate Light Meter
Sekonic L-308X-U Flashmate Light Meter
This light meter allows you to precisely measure the light in any situation, making it easy to apply the Sunny 16 Rule for perfect exposures every time.
Buy from Amazon

[ExpertPhotography is supported by readers. Product links on ExpertPhotography are referral links. If you use one of these and buy something, we make a little bit of money. Need more info? See how it all works here.]

Sunny 16 Rule in the Digital Era

In the past, the Sunny f16 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 nowadays, built-in light meters are present in every device. From the cheaper camera phone to the pro-graded DSLR camera.

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

  • It makes you work faster in manual 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 keep practising my ability to reading light. Here, I bet on the Sunny 16 and was right.

How Does the Sunny 16 Rule Work?

The Sunny f16 rule states that, on sunny days, at an aperture of f/16, your shutter speed is the inverse of your ISO value.
This means that if you are at, say, aperture f/16 and ISO 100, your shutter speed should be 1/100 seconds. This is one of the easiest photography rules to remember.
It is a great starting point, as 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 f16 rule.

The Exposure Triangle

The Sunny-16 rule works on the so-called exposure triangle. Your image exposure is the combination of 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.
The Exposure Triangle. Shutter Speed, Aperture and ISO – together they determine the image exposure.

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

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

The over- or under-exposure appears in the brackets.
Not all cameras and lenses allow you to shoot at f/16 or narrower apertures. For example, my Sony RX100 does not close more than f/11. Micro four-thirds cameras start to suffer from diffraction over f/8.

Similar Rules

It is not always sunny outside. Some days are pretty dark, and the sunny f16 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: when photographing in an open field during a sunny day;
  • Slight Overcast-11 Rule: when the sky is variable;
  • Overcast-8 Rule: cloudy weather, but not dark;
  • Heavy Overcast -5.6 Rule: bad weather, maybe rainy;
  • Sunset-4 Rule: 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 principle is the same as for the Sunny-16. In overcast conditions, follow the Overcast-8 Rule. To achieve a shutter speed of 1/100s, you should set your camera to f/8 and ISO 100.
Let’s see a couple of examples:

  • A classic light that 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.

  • A typical situation 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

To estimate which rule best matches the light conditions, look at shadow hardness. Actual sky conditions can be misleading.
In this photo, the sky looks great and clear, but some clouds are blocking the sun. As you can see, there are no shadows on the ground.

In these conditions, the light meter of my Sony RX100 Mk II camera tells me that a balanced exposure is obtained at ISO 100, f/11 and shutter speed of 1/100s.
This is the Slightly Overcast-11 rule.

Photo of a train pulling into a railway station on a day with blue skies and clouds
While the sky suggests the Sunny f16 rule should apply, 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 the 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
One of the best use of these rules is by applying them you will get fluent in reading light and shadows 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 different factors, and there are no bulletproof rules. This is why it’s important to know how to read the light, 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. However, the in-camera light meter is telling me that to have a shutter speed that is the inverse of my ISO (i.e., 1/100s).
Instead, I should use an aperture of f/5.6, and not f/16 as the hardness of the shadows would suggest.
Why? Because due to the strong foliage, the scene is rather dark. Compare it to the brightness of the image 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.


The modern digital photographer does not need to memorise these rules, thanks to the in camera light meter. But practising 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 practising right away! Take a look out the window: is that ‘use the sunny 16 rule weather’ or something else?

Sekonic L-308X-U Flashmate Light Meter
Sekonic L-308X-U Flashmate Light Meter
This light meter allows you to precisely measure the light in any situation, making it easy to apply the Sunny 16 Rule for perfect exposures every time.
Buy from Amazon
Show Comments (3)