What is the Sunny 16 Rule and Why Should You Learn It? by Jen Golay

Written by Jen Golay

If you’ve been in the film photography world for a while, then I’ll bet you’ve heard someone make mention of the Sunny 16 Rule. If not, well then you have now!

This is one of the most basic rules of thumb in photography, and knowing it and how to use it is invaluable for those moments when you’ve forgotten your light meter, if your internal light meter goes out, or if your meter is no longer reliable.

Knowing this rule and how to make it work for you will also make you a better photographer because you will learn how to read the available light and translate it to a pretty accurate exposure all without a light meter!

So, what is this amazing rule, and how does it work?

What Is the Sunny 16 Rule?

The Sunny 16 Rule is a method for calculating exposure without using a light meter. It says for proper exposure on a clear, sunny day, set your aperture to f/16 and your shutter speed to 1/ISO (or the closest corresponding shutter speed). Your ISO will be the ISO of your film.

For example: If I had Ektar 100 film in my camera, the ISO would be 100, and I would set my aperture to f/16 and my shutter speed to 1/125th of a second. Or if I had Portra 400 film in my camera, I would set my aperture to f/16 and my shutter speed to 1/500th of a second.

Pretty simple right?

I can already hear the questions you’re having: That’s great, Jen, but what if it’s not sunny out? How does this help me? Or what if I don’t want to use f/16? What if I need a faster or slower shutter speed?

These are all great questions, and I have got the answers for you.

Remember that this is just a rule of thumb, which means it’s not hard and fast and that it is really just a starting point.

If you have a good exposure for an image, you can take that exposure and manipulate it to fit your creative needs. And that is what the Sunny 16 Rule is — a starting exposure.

Why Use the Sunny 16 Rule?

Taking the time to learn how to use and manipulate the Sunny 16 rule for different light situations and various apertures and shutter speeds will make you a better and more intuitive photographer.

Do you have to use it to be a good photographer? Of course not!

But really knowing and understanding the exposure triangle inside and out will help you unravel tricky photographic situations, and it will make you so much more confident as a photographer.

When I took my college-level photography and darkroom classes, we had to learn how to quickly evaluate a lighting situation as well as rapidly calculate reciprocal exposures. At first, doing this felt so difficult and confusing, but after practicing often it became second nature.

Of course, I could have kept letting my light meter or my camera’s light meter do this for me, but learning to do it for myself made me confident and less fearful that my images wouldn’t “turn out.”

I would love to give you that same confidence. And it starts with the Sunny 16 rule, the exposure triangle, and reciprocal exposures.

Exposure Triangle

What makes the Sunny 16 Rule so reliable and usable in difficult lighting situations is that it is based on incident light (the light falling on the subject) rather than reflected light (the method used by most camera light meters).

This means you don’t have to worry about compensating for very bright or very dark subjects or situations. The Sunny 16 rule is based on the exposure value (EV) system.

I am guessing that you’re probably already familiar with the exposure triangle, but in case you’re not, here is a very basic explanation.

Every exposure has three elements: film speed (ISO), shutter speed, and aperture.

In digital photography, all three of these variables can be manipulated in each frame to get a good exposure and to create certain creative looks (shallow depth of field, motion blur, etc.). However, in film photography, once you’ve loaded your film, your ISO remains constant, and the only variables you can change are shutter speed and aperture.

In a way, that makes the exposure triangle a little easier to work with—only two variables instead of three.

ISO is how light sensitive your film is.

Shutter speed is how fast or slow the shutter opens and closes.

Aperture is how big or small the opening in your lens is.

All three are measured in stops, and each stop lets in double or half the amount of light as the previous or following stops.

Shutter speeds are pretty self-explanatory: they are fractions of a second. ½ of a second is slower than 1/500th of a second.

Apertures are a little more confusing and are less intuitive. The numbers correspond to how large or small the aperture of your lens is, and what makes them so confusing to many beginners is that the larger the number, the smaller the opening.

But to simplify this concept and to help you remember this, think of f/stops as fractions too. (They are in fact fractions! Focal length/diameter) So 1/22 is definitely smaller than 1/5.6.

When you use your light meter, whether in your camera or hand-held, it measures the light reflected by the subject (reflective) or the light falling on the subject (incident).

You will have already dialed in the ISO you’re using, and then you will dial in the aperture and shutter speed you need to zero out the in-camera meter. Or perhaps you also have dialed in the aperture you want to use in your hand-held meter based on how shallow or deep you want your depth of field, and the light meter will calculate what shutter speed you need to use to get a good exposure.

But how does your light meter figure this stuff out?

The three sides of the exposure triangle all correspond to one another and adjusting one variable will mean adjusting at least one other variable.

As we said earlier, because we are shooting film, our ISO will remain constant. Shutter speed is how fast or slow the light is let into the camera and the aperture is how big the opening is.

A fast shutter speed will usually require a larger opening to let in enough light, while a slower shutter speed will need a smaller opening to not let in too much light. You can have more than one good exposure due to the shifting values on the exposure triangle, and those other exposures are called equivalent or reciprocal exposures.

But before we take a look at those, let me remind you of the whole stops used in film photography.

Common Whole Stops in ISO, Shutter Speed, and Aperture

If you have a digital camera or even one of the later film camera models, you have the option to have shutter speeds and sometimes apertures to change in partial stops, and that’s great for even more dialed in exposures whether you’re using the Sunny 16 Rule or not. But most film cameras operate in full stops.

Here are the full shutter speed stops from the slowest to the fastest shutter speeds:
B (Bulb) 1, ½, ¼, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000, 1/2000, 1/4000

Full aperture or f/stops can go as low as f/1.2 or even f/.95 on a few rare lenses, but most range from f/1.4 to f/22.

Here are the full aperture stops for most lenses used with film cameras from the smallest to the largest aperture:
f/22, f/16, f/11, f/8, f/5.6, f/4, f/2.8, f/2, f/1.4

Remember that each stop either doubles or halves the amount of light that gets to your film.

For example: f/2 lets in twice as much light as f/2.8. Or f/2.8 lets in half the amount of light as f/2.

In shutter speeds, 1/30th of a second lets in twice as much light as 1/60th of a second. Or 1/60th of a second lets in half as much light as 1/30th of a second.

You really don’t have to memorize ISO stops in film photography since you only change them by changing your film, but you do need to know what they mean.

Lower numbered ISO films (below ISO 400) are considered slow film and require more light. Higher numbered ISO films (above 400) are considered fast film and require less light. ISO numbers also work in double or halves.

Generally, you’ll find film ranging in ISO from 50-3200: ISO 50, 100, 200, 400, 800, 1600, 3200.

Reciprocal Exposures

There can be more than one good exposure depending on how you change the variables in the exposure triangle.

For example, if you decrease the amount of light coming into the lens by stopping down your aperture, you’ll need to increase the length of time the shutter is open.

Or if you decrease the amount of time your shutter is open, you’ll need to open up your aperture to let more light in.

Let’s look at some specific examples.

ISO: 400
Shutter speed: 1/1000th of a second
Aperture: f/4
To calculate the reciprocal exposure if you change the shutter speed to three stops slower (to 1/125th), you’ll have to stop down the aperture by three stops. The new exposure is 1/125th of a second at f/11.

Here’s another example:
ISO: 800
Shutter speed: 1/125th of a second
Aperture: f/16.
To calculate the reciprocal exposure if you change the aperture to three stops wider (to f/5.6), you’ll have to speed up your shutter speed by three stops. The new exposure is f/5.6 at 1/1000th of a second.

Using the Sunny 16 Rule When It’s Not Sunny

Let’s get back to answering those questions we had about using the Sunny 16 rule in other lighting situations or with different apertures and shutter speeds.

You don’t need a sunny day to use the Sunny 16 rule if you know some basic stop differences for other types of light and you know how to calculate reciprocal exposures.

For each of the following lighting situations, you’ll need to change your exposure by one stop from Sunny 16:
Sunny: 0 stops
Partly Cloudy: 1 stop
Cloudy: 2 stops
Overcast: 3 stops
Dark Skies: 4 stops
Low Light: 5 stops

You can also think of these lighting situations in terms of shadow definition:
Sunny: Distinct shadows
Partly Cloudy: Shadows with soft edges
Cloudy: Faint shadows
Overcast: No shadows or open shade
Dark Skies: No shadows, deep shade, sunset
Low Light: No shadows

In lighting situations with snow or a lot of sand, bump your aperture up to f/22 as a starting point instead of f/16.

Sunny 16 Rule Cheat Sheet

ISO: The ISO of your film
Shutter speed: 1/ISO
f/Stop:

Make Your Own Cheat Sheet

You can make your own cheat sheet based on how you like to shoot.

For example, if you mainly keep your aperture constant, your cheat sheet might look like this if you’re shooting with ISO 100:

Here’s another example cheat sheet if you like to keep your shutter speed constant and vary your aperture if you’re shooting with ISO 400:

Calculators and Apps for the Sunny 16 Rule

After encouraging you to learn to do all of the calculations on your own and make your own cheat sheets, I am still going to share with you a couple of automated ways to use the Sunny 16 Rule. They will help you check your work without having to take copious exposure notes and matching them to your developed images to see if you got it right.

You can use these to check your own calculations before pressing the shutter button. Or to just practice calculating reciprocal exposures.

Some of them are digital apps or websites and some of them are good old fashioned analog charts or wheel calculators. I hope you find them useful as you get to know and use the Sunny 16 Rule.

This website calculator from Analog Cafe is great for doing the work for you, but also helping you see how the exposure values change depending on which variable(s) you change. It takes into account your film speed (ISO), shutter speed, aperture, and lighting situation. And it lists the exposure value differences.

This Sunny 16 Exposure Calculator for Apple iOS iPhones will do the same thing for you on the go. Again, it’s great to help you check your work if you want to practice. It will also give you + or – exposure values if you like to consistently overexpose your film to get the “light and airy” look. I believe the Sunny 16 app on Google Play will do something similar if you’re an Android user.

Here are two different paper exposure wheels if you want to go truly retro and not use a website or an app. This one from The Phoblographer is geared specifically for the Sunny 16 Rule, while this one is Ilford’s pinhole exposure calculator. All you need to do is print the component parts and assemble them with a split spinner.

Thank you so much, Jen! Jen is a regular contributor here at Shoot It With Film, and you can check out her other articles here, including 15 Must-Have Film Photography Accessories and What is a Rangefinder? And is It the Right Film Camera for You?.

You can also check out more of Jen’s work on Instagram.

Leave your questions about the Sunny 16 Rule below in the comments!

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Jen Golay

Jen Golay is a senior portrait and travel film photographer and a regular contributor for Shoot It With Film. Find her other articles here, such as How To Shoot Kodak Gold 200 and Olympus Pen F Half-Frame Film Camera Review.

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