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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. It’s actually really logical. The sunny 16 rule states that if it is 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 will have a correctly exposed image.

Obviously, it’s not that simple. But it is a good rule of thumb and an excellent starting point for setting exposure. If you haven’t given manual mode a go yet, this is the easiest way to give it a go.

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

What if it’s not sunny?

Using f16 as a starting point for your exposure (with ISO set to 100 and shutter speed set to 1/100) adjust 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 best aperture to use in other conditions. Don’t forget though, that this is just a starting point for setting exposure. Check your exposure meter before taking the shot.

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.
  Sandy beach on a cloudy day

But I don’t want to shoot at f16

Well, here’s where it gets really interesting, because those settings 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.

Let’s say you like shooting at f8

It’s an easy adjustment if you bear in mind how the exposure triangle works – adjust one of the settings one way and 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 (f16, f11, f8) – 2 stops more light entering the lens.

So you need to reduce either your ISO by 2 stops or speed up your shutter speed by 2 stops to keep the balance the same (2 stops less light).

Your shutter speed would therefore need to be increased to 1/400 or your ISO would need to be reduced 2 stops less than 100. On my Nikon that reads as L10. In most situations I would choose to change shutter speed.

Let’s look at it another way

Maybe shutter speed is your priority and you want to shoot slower than 1/100 to maybe blur water.

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.

That’s the theory bit over. Let’s see the sunny 16 rule at work…

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

The shutter speed went up 2 stops from 1/100, so I opened up the aperture by 2 stops from f16 for the same exposure.

Buoy on a sandy beach

Here’s another one.

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

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If you have any questions about exposure and the sunny 16 rule, let us know in the comments.

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