The Sunny 16 rule is another one of those rules of thumb carried over into the era of digital photography from the heydays of film photography. It is a quick and easy way to get your camera settings right for a sunlit day’s shoot.
Basically, all it says is:
The Sunny 16 rule suggests using the reciprocal of the ISO value used, for the shutter speed value while keeping the aperture value fixed at f/16 for shooting subjects in direct sunlight.
Let me explain that a little further.
First and foremost, I would like to draw your attention to the fact that the Sunny 16 rule or the Sunny f/16 rule is one which is about estimating correct image exposure. What the ‘rule’ suggests is, setting the camera to an aperture value of f/16 and then using the reciprocal of the ISO value we use as the shutter speed.
If you are stumbling over the word reciprocal, all it means is:
The reciprocal of a number ‘x’ is 1/x.
So after dialing in the aperture value f/16, if you decide to use ISO 100 you should use 1/100th of a second shutter speed to ensure a correctly exposed image.
Now, keeping the aperture fixed at f/16, if you want to use some other value for the ISO, you should also consider changing the shutter speed accordingly to maintain the same level of exposure.
Simple logic?
Just to get you in the groove, here are some more examples of camera settings which are all set using the Sunny 16 rule:
- Aperture: f/16, ISO value: 200, Shutter speed: 1/200th of a second
- Aperture: f/16, ISO value: 300, Shutter speed: 1/300th of a second
- Aperture: f/16, ISO value: 500, Shutter speed: 1/500th of a second
It’s basically a balancing act between the ISO value you choose and the shutter speed of the camera.
Notice that the aperture value in all the above settings is kept constant at f/16. Do you really have to keep it fixed like that?
No! Not really.
Just keep going and I will tell you how you could tinker with the aperture value too, without messing up the exposure.
Validity In The Digital Era
I know what you are thinking. Do I really need to learn yet another archaic rule, just set the exposure? Doesn’t my camera already come with a light meter?
And you would be right, on both accounts.
All modern digital cameras today come with excellent light meters which are capable of metering and suggesting the best possible settings for nearly any situation you are ever likely to come across.
So why bother learning the Sunny 16 rule and setting the exposure manually?
Truth be told if you are an amateur shooter who enjoys shooting images every now and then and do not really care about artistic choices or complex compositions, you really do NOT need to learn this old ‘rule’ at all. Your camera is smart enough to make all these decisions for you.
This rule comes from the time of film photography. The younger generation wouldn’t know much about it, but it was a pretty unforgiving time.
Any photo you took could only be seen after you finished shooting the entire film roll, developed it, and then printed the photos out. And all this would take at least a couple of weeks. So, any mistakes made during the making of the images were almost never forgiven.
There were no in-camera light meters. No auto mode to save you from the pain, and the exposure for every image had to be dialed in manually every single time.
Just think about it for a moment. You take an image on your phone today and then you are allowed to look at it only after a week. How would it make you feel? Would you even remember you took it, after a week’s time?
Not to mention the enormous cost of films and the money required to get them processed later.
Hence, getting things right in-camera was of paramount importance. There simply was next to no margin for error. If you make a mistake, you had to pay for it….literally!
There was yet another major reason for ‘rules’ like the Looney 11 and the Sunny 16 to come up.
Film rolls were of a single ISO value only.
What this means is that you could only have a single roll of film in your camera at one time and the roll of film was rated for a single value of ISO only. In other words, you could NOT change the ISO value on the fly for every other photo, like you do today.
The ISO value was defined and fixed by the film roll you had in your camera.
Now imagine using the Sunny 16 rule with a film camera.
So you have the aperture set at f/16. The ISO value is defined by the film you are currently using, say it is ISO 100 presently. So all you have to do now is set the shutter speed to 1/100th of a second, and you are set to shoot the entire day without even touching the settings dial.
Now that is some peace of mind.
It, at least, has the promise that you would not have all black frames or washed out details at the end of the day when you finally decide to reap the soil and develop the film roll.
Owing to all these ‘hostilities’ of the bygone times, it is no wonder that photographers came up with all these nifty little ‘rules’ to help alleviate the confusion and make sound decisions resulting in good images at the end of the day.
Mental Meter
For me personally, I believe you do not need the Sunny 16 rule to tell you proper exposure settings. Your camera’s TTL (Through The Lens) metering system is more than capable of performing such calculations.
Having said that, I would also like to strongly urge any new photographer, interested in immersing herself/himself in the art of photography and in creating something more than mere snapshots, to understand this ‘rule’, use it and on its back, and build a solid understanding of what actually happens inside your camera.
There are a million people out there driving cars, but very few of them know what goes on under the hood. To be fair, you do not even need to know that to drive a car and drive it well. But some of us are nosy and no amount of knowledge satiates us.
Learning the Sunny 16 rule is probably something like that.
Expanding The Rule
I promised in the beginning that I would show you how you can dial in an aperture value other than the prescribed f/16, this rule’s namesake, and even then manage to get the exposure right.
Well, here it is.
It all comes down to this concept called the exposure triangle, comprising the three primary building blocks of any photograph ever taken:
If this is the first time you are coming across the term exposure triangle, I highly recommend this article which explains in its entirety the dynamics of the three fundamental elements and how you can use them to make an image. Exposure Triangle Understanding Aperture, Shutter Speed & ISO.
Now comes the manipulation.
So now as we are aware of the exposure triangle, we know that dialing in ANY set of camera settings is nothing but a balancing act based on many factors such as the amount of light available, motion in the frame, depth of field required, etc.
The Sunny 16 rule prescribes the aperture value of f/16 since it gives the photographer a good amount of depth of field to play with and also allows normal ISO values such as ISO 100 and ISO 500 to adjust easily against the corresponding shutter speed change.
Had the aperture value been anything like f/1.8, the balancing of the shutter speed and ISO wouldn’t be so poetic after all.
Why…you ask?
Okay, let’s think of a hypothetical set of camera settings.
- Aperture value: f/11, Shutter speed: 1/100th of a second, ISO: 100
You will notice here that the settings above would allow one-stop of extra light into the camera than the Sunny 16 rule suggests. This is due to the selection of the aperture value; f/11 instead of f/16.
Now direct sunlight is uniform in light intensity in all parts of the world. So in theory allowing the extra stop of light into the camera through the aperture will cause the image to be overexposed by a stop.
So what do we do now?
It’s simple really.
All we have to do is compensate for the extra light and restrict it using the other two handles we have, namely shutter speed and ISO.
Since we are using an ISO value of 100 which is the lowest in most cameras what we can do is increase the shutter speed to reduce the light by a stop.
But by how much?
To cut light by a stop we need to increase the shutter speed to 1/200th of a second in this case.
Wondering how I calculated the shutter speed value? Read How To Be An Exposure Calculating Ninja Right Now, it is all you will ever need.
The underlying principle for exposure calculations is actually very simple at its core.
Everything remaining constant if you allow some extra light coming in through one of the three channels, you need to compensate for that extra light by reducing an equal amount of light using any of the other two channels. This would lead to the exposure remaining constant and give you a well-exposed image.
For the exact figures, you, unfortunately, have to do the math. But I assure you that it is simpler than you think it is.
Once you get the hang of it and understand the clicks of the command dial of your camera, it all becomes second nature. Read the article I suggested earlier, it explains step by step the entire process.
Just A Ballpark
Now that you have a sufficiently strong understanding of the Sunny 16 rule, I hope you realize that the ‘rule’ is only a guideline. A suggestion, if you will. It is in no way supposed to be perfect for all images shot under the sun.
It is just a short and simple way to get you as close as possible to the correct set of settings without interfering with the artistic wing too much.
The sun is at constant power at all times and hence could be treated as a uniform, homogeneous source of light. But there are always exceptions. Cloud cover, time of the day, presence of fog or mist, etc. all affect the amount of sunlight available and its quality.
So take this new ‘rule’ only as a suggestion rather than the gospel.
As the sunlight changes, you can and should accommodate for it using any one or more of the three elements of the exposure triangle.
Other Similar Rules
Just like the Sunny 16 you just learnt about, there are some more ‘rules’ which were designed to facilitate the selection of camera settings. Some of them are as follows:
- Snowy 22
- Slight Overcast 11
- Overcast 8
- Heavy Overcast 5.6
- Sunset 4
If you look closely I believe you will see a pattern in all of them?
Do you see it?
No?
Alright, here it is…All the so-called rules mentioned above function exactly the way the Sunny 16 rule does. You dial in the number written next to the rule as the aperture value and then balance the ISO and the shutter speed like you did before.
If you notice carefully you will see that as the amount of available light goes down, the rules mentioned above are all compensating using the aperture value.
Slight overcast suggests using an aperture value of f/11 and Heavy Overcast f/5.6. By shifting the aperture from f/11 to f/5.6 (which is one stop of light), the rule is just trying to open up the aperture hole to try and get in some more light into the camera.
As the light falls, the aperture value falls (meaning larger aperture hole) too and vice versa.
Makes sense right?
If you understand the exposure triangle well enough, I doubt you will ever need to even know these crutches at all.
Point To Remember
- The Sunny 16 rule only deals with exposure of an image. Keep other factors such as depth of field, image noise, and subject motion in mind before making a decision about the settings.
- Whenever in doubt about your exposure, always check with your camera histogram.
- If you are still unsure about the correct exposure, use exposure bracketing and take more than a few images to cover your base.
- Sunny 16 is based on incident light rather than reflected light.
- It is also intended for subjects in direct sunlight only. So even if you are indeed shooting on a sunlit morning, if your subject is in the shadows, you would need to change the settings to accommodate for the shortage of light.
If you are a beginner at this point in time then I would suggest you learn and adapt the Sunny 16 rule, and then as soon as possible use it to expand on its bases. Focus on learning the exposure triangle and use the ‘rule’ only as a stepping stone.
Learn more about light, its qualities, and properties. How it behaves, how you could modify it and mold it to make better images. And that would last you a lifetime.
I hope I have been of some help to you in introducing the concept of the Sunny f/16 exposure rule and you’ve got something out of it.
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