Have you heard of the Sunny 16 rule and wondered what it’s about?
Have you ever wondered how people measure exposure using cameras without light meters?
If you answered yes to either question or want to learn how to ‘guess’ the exposure just by looking at a scene – this is the article for you.
I’ll explain the Sunny 16 rule and how to use it.
I’ll also show you how to use the reciprocity law to change both shutter speed and aperture to gain creative control.
(This is when you want a shallow depth of field, capture motion blur, etc.)
Lastly, I’ll answer popular questions like ‘Is the Sunny 16 Rule still useful in the digital age?’
If I’m piquing your interest, keep on reading!
Table of Contents
What Is the Sunny 16 Rule?
The Sunny 16 rule is a metering system that calculates the correct exposure without a light meter. This might sound weird to you because you usually use the camera’s light meter, right?
All modern cameras have an in-camera light meter – except for some Lomo or some unique models. However, this wasn’t always the case.
At most, the cameras aimed at amateur users had an exposure guide in the back. This showed how to adjust the camera settings based on the light conditions.
This is pretty much what the Sunny 16 rule is about. You adjust the exposure triangle based on the weather and lighting conditions.
This means that it uses incident light – just like an external light meter. So, it’s more accurate because most camera light meters use reflective light.
Therefore, the camera’s light meter can be misled by difficult subjects.
This is because the light reflected from dark subjects might cause the camera to overexpose the picture. On the other hand, very bright subjects may confuse the in-camera light meter and cause it to underexpose it.
In digital photography, even if the camera’s meter over or underexposes the photo, you can see it immediately. So you can make the necessary adjustments to achieve the correct exposure.
Ok, but what happens if you don’t have a light meter? Well, that’s when the Sunny 16 Rule comes into play. The rule says the shutter speed should be reciprocal to whatever ISO you use. Then, you set the aperture to f/16 for a sunny day.
If the weather is not sunny, you should adjust the aperture, leaving the exposure triangle’s other factors always at the same value.
Of course, this means you must use the camera in manual mode, and it’s mostly useful for outdoor photography.
How to Use the Sunny 16 Rule
You usually set the ISO with a digital camera after deciding the aperture and shutter speed. You start with the shutter speed if you’re concerned about motion or with the aperture if you prioritize the depth of field.
To use the Sunny 16 rule, you need to start with the ISO value. This is because, in film photography, you can’t change the ISO on every picture. You could only choose the film speed, which would be the same for the entire roll.
However, back to using the Sunny 16 rule. You need to use the camera in manual mode. Now, you start by setting the ISO.
If it’s a film camera, you choose the ISO with the film’s sensitivity. You can freely decide which ISO to use if it’s a digital camera. Then, set the shutter speed to the number that’s closest to the ISO value.
For example, the most common film is ISO 400. Then, the closest shutter speed would be 1/500. If you’re shooting with an ISO of 100, then set the shutter speed to 1/160, and so on.
Since the exposure triangle uses three factors and you already have ISO and shutter speed, then you need to set the aperture.
The Sunny 16 rule says that when you’re shooting on a sunny day, and your subject receives direct sunlight, the aperture should be at f/16.
As you know, each one of the camera settings has a different impact on your photo. The shutter speed can either freeze a moving subject or capture motion blur.
The aperture controls how much of your image is in focus. This is known as the depth of field.
So, what happens if you want to change the depth of field or the shutter speed? Does the Sunny 16 rule work?
Yes, you can still use the Sunny 16 rule and change the aperture or the shutter speed. You simply have to apply the reciprocity law.
What is reciprocity, and how does it work with the Sunny 16 rule?
Reciprocity is the basic rule that guides the exposure triangle. Each stop either doubles the light or allows half the amount of light. Therefore, moving one of the settings in one direction can be compensated by moving the other in the opposite direction.
So, if I set the shutter speed two stops slower, I need to narrow the aperture by two stops and get a good exposure.
Let me give you a practical example of applying the Sunny 16 rule.
Let’s say you want to make a portrait shot with a blurred background on a sunny day. If you have an ISO of 400, and a shutter speed of 1/500, the original rule calculated an aperture of f/16 for correct exposure.
However, that aperture won’t blur the background. So, you need to use a wider aperture to achieve a shallower depth of field.
The exact aperture value depends on the focal length and the distance. On average, an f/4 should result in a shallow enough depth of field.
You’ll have too much light once you change the aperture from f/16 to f/4. To achieve the proper exposure, you must compensate with other exposure settings so that less light comes into the camera.
There are four stops in between those two apertures. So, by the law of reciprocity, you can get the perfect exposure by making the shutter speed four stops faster.
Therefore, 400 ISO, 1/8000, and f/4 are the equivalent exposure of 400 ISO, 1/500 shutter speed, and f/16 aperture.
You can also adjust the ISO setting if you prefer. For example, you can use ISO 100, 1/2000, and f/4 to get the proper exposure.
What If It’s Not So Sunny?
As the name says, the Sunny 16 rule is based on shooting on a sunny day. Unfortunately, we don’t always get sunny days. So, what happens when the weather conditions change? Can you still use the Sunny 16 rule?
The answer is yes. You can use the Sunny 16 rule as a starting point – then, you have to adapt it to the weather and lighting conditions.
As you would do on a bright sunny day, you must start by setting the ISO. Then, set the correct shutter speed in relation to the ISO you’re using.
So far, nothing has changed – that’s because you need to make adjustments in the aperture to achieve correct exposure.
Since it’s not so sunny, there’s less available light. This means that you need to use a wider aperture to let in more light than you would on sunny days.
Here’s a table you can use as a guideline to achieve good exposure.
- Cloudy day, not yet overcast – f/11
- Overcast – f/8
- Dense overcast – f/5.6
- Sunset or standing in the shade outdoors – f/4
As you can see, things can get tricky because the different light conditions aren’t so clear-cut. When does it pass from cloudy to overcast? When does the overcast become too dense?
So, the Sunny 16 rule is still a good parameter, but it may be less accurate. Some people prefer to use shadows to understand how to apply the rule.
Hard shadows correspond to Sunny 16, while no shadows mean f/5.6, otherwise known as dense overcast. This means that f/8 and f/5.6 correspond to lighter, less-defined shadows.
There is one exception that you should know. So far, all the adjustments were made to open the aperture and let in more light.
When you’re shooting a snowy landscape, you need to close the aperture by one stop. This is because the light is very bright. So, even if it’s not sunny, it will reflect whatever available light.
So, this exception to the Sunny 16 rule is known as the Snowy 22 rule. Yes, you’ve guessed it, you need to set the aperture to f/22. This way, it will enter half as much light as it would with an f/16. This rule also applies to sand.
One last thing to consider is that you should add one stop whenever your subject is backlit.
Sunny 16 Rule Examples
The image above was taken with a Nikon D750 and a 100mm lens. The exposure was ISO 800, 1/2000 shutter speed, and f/11 aperture.
As you can see, it followed the Sunny 16 rule and used the reciprocity law to adjust the settings. Let’s see how.
According to the Sunny 16 rule, the closest shutter speed should be 1/1000 sec. Given that it’s a sunny day, the aperture would be f/16.
In this case, the photographer chose a faster shutter speed – probably to freeze the movement of the bicycles.
So, the shutter speed is faster by one stop – 1/2000 sec. This means that there’s half the light coming in. The reciprocity law indicates that we can compensate for this loss by adjusting any of the other two factors from the exposure triangle.
In this case, the author decided to use the aperture. Therefore, the aperture is one stop wider – f/11.
In conclusion, the Sunny 16 rule indicated an exposure of ISO 800, 1/1000 shutter speed, and f/16 aperture. By the reciprocity law, the photo was made with ISO 800, 1/2000 shutter speed, and f/11 aperture.
Let’s see another example. This image was taken with a Canon EOS 5D MarkII. The exposure was ISO 100, 1/2000, and aperture f/4.
There are a few clouds on the horizon. However, the sand and water are very reflective – so they can compensate. Overall, we can all agree it’s still a bright sunny day.
However, it does recall a judgment call from the photographer – it’s not so straightforward anymore. You must also apply the reciprocity law to realize that this photo follows the Sunny 16.
Following the rule to the letter, the exposure should be ISO 100, 1/125 sec, and f/16. The author chose not to use this but found more appropriate settings for the situation. This is because you need a fast shutter speed to freeze the waves.
There are four stops between 1/125 and 1/2000. By reciprocity, the aperture needed to be four stops wider. That’s why f/16 turns into f/4.
Basically, ISO 100, 1/125 sec, and f/16 are equivalent to ISO 100, 1/2000, and f/4.
Before, we discussed whether you can use the Sunny 16 rule if it’s not sunny. So, let me give you an example to show you what we learned.
According to the table, you can find in the “What if it’s not sunny” section, you need to set the aperture to f/4 to shoot a sunrise or a sunset.
This photo’s exposure settings are ISO 200, 1/125, and f/5.6. So, it follows the rule accurately with a one-stop reciprocity adjustment.
The adequate shutter speed for ISO 200, according to the Sunny 16 rule, is 1/250 because it’s the closest number to 200.
The author decided to use 1/125, which is one stop slower. To compensate, the aperture needs to be one-stop smaller. So, instead of using f/4, the author used f/5.6.
What is the Sunny 16 Rule for ISO 160?
Most cameras allow you to use half a stop or even a third. So, you might see 1/160 or 1/180 and think that’s the closest value to ISO 160.
However, the Sunny 16 rule considers full stops. So, the closest shutter speed to 160 would be 1/250.
What is the Sunny 16 Rule for ISO 200?
Following the Sunny 16 rule, the proper exposure for a sunny day with ISO 200 is 1/250 and f/16.
Don’t be misled if you see 1/200 in your camera – that’s a third of a stop. Using this, you must compensate with a third of a stop in the aperture value.
What is the Sunny 16 Rule for ISO 400?
The Sunny 16 rule for ISO 400 is 1/500, f/16. If you use 1/400, then you would need an aperture of f/18.
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What is the Sunny 16 Rule for night?
I should note that there is something called the Loony 11 rule. However, this is to help astrophotographers to shoot the moon’s surface. It’s not used to calculate the exposure of subjects hit by moonlight.
Sunny 16 Rule Cheat Sheet
Most film cameras used to have an exposure guide in the back with some version of how to use the exposure settings. They were primarily based on how to use the Sunny 16 rule.
Following that tradition, here’s a Sunny 16 Rule cheat sheet that sums up everything we’ve said so far.
|100||f/22 – 1/125||f/16 – 1/125||f/11 – 1/125||f/8 – 1/125||f/5.6 – 1/125||f/4 – 1/125|
|200||f/22 – 1/250||f/16 – 1/250||f/11 – 1/250||f/8 – 1/250||f/5.6 – 1/250||f/4 – 1/250|
|400||f/22 – 1/500||f/16 – 1/500||f/11 – 1/500||f/8 – 1/500||f/5.6 – 1/500||f/4 – 1/500|
|800||f/22 – 1/1000||f/16 – 1/1000||f/11 – 1/1000||f/8 – 1/1000||f/5.6 – 1/1000||f/4 – 1/1000|
I have a meter, do I need the Sunny 16 rule?
You don’t need the Sunny 16 rule if you have a light meter. It’s still helpful to use the rule and compare it to the results given by the light meter. This way, you’ll learn how to evaluate the light in case you need it sometime when you don’t have the meter with you.
What do I listen to: the meter or the Sunny 16 rule?
The camera’s light meter reads the reflected light, and the Sunny 16 rule accounts for incident light, making it more accurate. However, the rule is not as precise when it’s not sunny.
So, if you have an external light meter, go with that one. If not, listen to the Sunny 16 rule when it’s sunny and to the camera’s built-in light meter if it’s not.
However, as you gain more practice, you’ll be able to rely more and more on your expertise and apply the Sunny 16 rule very accurately.
Is the Sunny 16 Rule accurate?
Yes, the Sunny 16 rule is accurate when shooting on a sunny day. The problem is that even a couple of clouds can alter the amount of light, even if it’s not perceptible by the naked eye.
This is even more problematic if there are more clouds, shades, overcast, etc. Then, it’s more difficult to accurately determine whether you need to use an f/11 or f/8, and so on.
Is the Sunny 16 rule just for film cameras?
Not necessarily. The Sunny 16 rule dates back to the film era because it wasn’t as common that the camera would have a built-in meter.
Indeed, you wouldn’t have a light meter if you weren’t a professional photographer. So, the Sunny 16 rule made a lot of sense when shooting film.
Now, all digital cameras have a light meter, so you don’t need to guess the reading. However, this doesn’t mean that it wouldn’t be accurate if you apply the Sunny 16 rule.