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Have you heard of the sunny 16 rule?

If not, it may seem like a really odd name for a rule. Well, it’s not actually a rule, but more of a technique. The sunny 16 rule is in fact a really logical technique for metering exposure without using your camera’s exposure meter or a light meter.

What is the sunny 16 rule?

The sunny 16 rule states that if it’s a sunny day, there’s a very good chance that if you set your ISO to 100, your shutter speed to 1/100 and….here’s where the name on the tin comes from….your aperture to f16, you’ll have a correctly exposed image. For this reason it is also known as the sunny f16 rule.

What, that’s it? No.

But that’s not all

In addition to that, if you change your shutter speed to 1/200, change your ISO to 200 and keep your aperture at f16, you’ll have the same exposure. So, the sunny 16 rule states that just change shutter speed and ISO, equally and keep aperture the same. Handy if you need a faster shutter speed.

In other words, your shutter speed should be the inverse of your ISO. If your shutter speed is 1/400, set ISO to 400 etc. Why would you do that? I’ll explain in a moment.

Obviously, there’s more to exposure than that. But the sunny 16 rule is a good guesstimate and an excellent starting point for setting exposure outside during the day. If you haven’t given manual mode a go yet, this is the easiest way to get started.

But actually, you can take the sunny 16 rule even further than this! Read on.

Learn about the exposure triangle here: The exposure triangle – why is it so important to know?

What if it’s not sunny?

The sunny 16 rule is not just for sunny days. It works in the same way in not so sunny conditions, but with different aperture settings.

If you set your ISO to 100 and your shutter speed to 1/100, adjust just the aperture according to this rough guide for different lighting conditions:

  • f22 – sunny and you’re in snow or on white sand
  • f16 – sunny
  • f11 – sunny and cloudy
  • f8 – cloudy
  • f56. – overcast
  • f4 – sunset or in the shade
  • f2.8 – dusk

Download and print out our handy guide for the aperture to use in different lighting conditions. Don’t forget though, that this is just a starting point for setting exposure. Check your exposure meter before taking the shot.

Further reading: Understanding the exposure meter – controlling exposure part 1

Reflection and direction of light

Both reflection and direction of light can get in the way of this rule being ridiculously easy. When you put them together, it really does throw your exposure off. This is why the sunny 16 rule is a rule of thumb and not an exact science.

Water, for example, is a highly reflective surface, so if you’re shooting into the light on a wet beach (see below), the sunlight will bounce off the beach and into the camera, making for a very bright scene.

Turn the other way, so that the sun is behind you, and the light won’t be reflected back into your camera. It will, in theory, be a correctly exposed scene.

Overexposed image of a sandy beach on a cloudy day

These photos were taken seconds apart with the same settings: ISO 100, shutter speed 1/100, aperture f16.

The only thing that changed was my direction. Shooting into the sun on a wet beach made the above image overexposed, while turning 180 degrees so that the sun was behind me correctly exposed the below image.

Advanced sunny 16 rule

Here’s where the sunny 16 rule gets really interesting, because those settings of…

  • ISO 100
  • SS 1/100
  • F16

…are simply the basis from which to set your exposure. Just because you’re outside on a sunny day doesn’t mean that you have to photograph at f16.

You might want to have a shallower or deeper depth of field than is achievable at f16. Alternatively, you might need a faster or slower shutter speed than 1/100. So let’s look at using the sunny 16 rule, but adjusting:

  1. aperture
  2. shutter speed

1. Aperture variations on the sunny 16 rule

For this you need to bear in mind how the exposure triangle works – if you adjust one of the settings one way, you need to adjust one of the other two settings an equal amount the other way.

Shooting at f8 instead of f16 is a 2 stop increase in the size of the aperture (f16, f11, f8)…there’s 2 stops more light entering the lens.

So, to keep the exposure balance the same (with 2 stops less light) at f8, you need to either:

  • reduce your ISO by 2 stops to less than 100 or
  • speed up your shutter speed by 2 stops to 1/400

On my Nikon 2 stops lower than ISO 100 is L10. There’s only so far you can reduce the ISO, so in most situations I would choose to change shutter speed.

2. Shutter speed variations on the sunny 16 rule

If shutter speed is your priority and you want to shoot slower than 1/100 to maybe blur water for example…

In this situation, if you slowed your shutter speed down to 1/50 (1 stop more light), you would need to adjust your aperture the other way from f16 to f22 (1 stop less light) to maintain the same exposure value.

An example – how I apply the sunny 16 rule

I prefer not to shoot below 1/200 when handholding my camera and quite often I like to use an aperture of f4. So, for my preferences on a sunny day, I use the sunny 16 rule like this:

  • Aperture – f4 (4 stops wider than f16)
  • Shutter speed – 1/1600 (4 stops faster than 1/100)
  • ISO – 100

That’s the theory bit over.

Let’s see the sunny 16 rule at work…

Although it was a sunny/cloudy day, it was very bright with a lot of reflection, so I used f16 as the starting point instead of f11 (which is usually more suited to a sunny cloudy day).

Yellow buoy on a sandy beach

Above settings: ISO 100, shutter speed 1/100, aperture f16. Below settings: ISO 100, shutter speed 1/400, aperture f8

In the image below, the shutter speed went up 2 stops from 1/100 to 1/400, so I opened up the aperture by 2 stops from f11 to f8 to achieve the same exposure for both images.

Buoy on a sandy beach

Here’s another example. This time showing how I prefer to apply the sunny 16 rule.

Pebbles on a sandy beach

Above settings: ISO 100, shutter speed 1/100, aperture f16. Below settings: ISO 100, shutter speed 1/1600, aperture f4.

I wanted to blur the background, so I set my aperture to f4. This meant that I had to adjust my shutter speed by 4 stops as well, the equivalent amount the other way.

Pebbles on a sandy beach

As you can see, once you understand how to use the sunny 16 rule, you can adjust it to fit how you want to capture a scene without having to use a light meter. Although, as I said before, it always helps to double check it against your camera’s light meter. Just remember that there are circumstances that confuse your camera, so you might need to bear this in mind.

Further reading:

More advice for sunny days: 7 tips for photographing in bright sunlight

Why your camera’s exposure meter isn’t always correct: Understanding how exposure metering works

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