In this Photography 101 article, you’ll learn more about the famous Sunny 16 Rule.
The Sunny f16 rule helps you guesstimate which camera settings to use for a balanced exposure. As the name suggests, it’s for shooting outdoors during sunny days.
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Sunny 16 Rule in the Digital Era
The Sunny f16 rule or 16 rule was a must have in a film photographer’s bag of tricks. It is one of the best photography rules that you can have in the back of your mind.
But nowadays built-in light meters are present in every device. From the cheaper cameraphone to the pro-graded DSLR camera. This photography rule acts as a metering system when you dont have one.
Nonetheless, the Sunny 16 Rule can still serve you well in several ways:
It’s a useful exercise to improve your ability to read the available light. With a light meter app on your smartphone, you do not need to take any picture at all. Check the settings you would use against those suggested by the app.
I like to use the app Pocket Light Meter on my iPhone to keep practicing my ability to reading light. Here, I bet on the Sunny 16 and was right.
It makes it easier to experiment with film photography. For example, when shooting large format 6×6 film;
Yashica LM-MAT TLR 6×6 medium format film camera.
It makes you work faster in manual with your digital camera.
What Does the Sunny 16 Rule Say
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, f/16 and ISO 100, your shutter speed should be 1/100 seconds. As a rule of thumb, this is one of the easiest photography rules to remember.
This is a great starting point, as you will no doubt want to change your exposure settings based on the reflected light available.
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 you ISO, shutter speed or aperture to reach the correct exposure.
The Exposure Triangle. Shutter Speed, Aperture and ISO – together they determine the image exposure.
Say you’re using f/16, ISO 400 and shutter speed of 1/400s. You get the same exposure with the following settings combinations:
f/11 (+1EV), ISO 400 (0EV) and 1/800s (-1EV)
f/16 (0EV), ISO 800 (+1EV) and 1/400s (-1EV)
We’re only discussing image exposure. We’re not considering other aspects here, like image noise and depth of field.
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.
As you may know, it is not always sunny out there. Some days are pretty dark and the sunny f16 rule does not fit those conditions very well. For this reason, there are different rules depending on the weather.
Those rules are: Slightly Overcast-11, Overcast-8, Heavy Overcast-5.6, Sunset-4 and Snowy-22. The last one is for sunny days and snowy terrains.
The sunny 16 rule chart below illustrates the conditions for which the different rules apply:
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;
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, may be rainy;
Sunset-4 Rule: for typical sunset conditions.
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.
This is a typical situation for the Heavy Overcast-5.6 rule.
Forget the Weather, Read the Shadows
To guesstimate 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 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.
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 .
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 empirical and not exact, nor are they rigorous. 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.
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 the scene, due to the strong foliage, is, in average, rather dark compared to the brightness of the image below, taken only a few minutes later and under the same kind of daylight.
This image of an open ground, instead, follows the Sunny 16 rule. In general, open ground images are much brighter than those taken under the canopy of trees.
For those the use of these empirical rules is not that straightforward. And if this isn’t enough to convince you to use the Sunny 16 rule, check out this video of astronaut Chris Hadfield using the Sunny 16 rule from Space!
The modern digital photographer does not need to memorise those rules, thanks to the in-camera light meter. Practising with the sunny 16 rule is a great exercise to learn to read the available light – a must for any outdoor photographer.
And you can start practising right away! Take a look out the window: is that sunny 16 weather or something else?
A note from Josh, ExpertPhotography's Photographer-In-Chief:
Thank you for reading...
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