It is a perfect sunny day and you feel like clicking some landscape photos, but then you realize that you are not carrying a handheld light meter. The only option you are left with is to manually set the exposure of your digital camera by going through the shutter speed and the aperture. The Sunny 16 rule is a savior in this situation, as it helps you to determine the perfect exposure settings on a sunny day.
Related post: Understanding The Light Meter: Incident and Reflected

How does the Sunny 16 rule work?
In order to get the perfect exposure on a bright sunny day, simply set the aperture value of your camera lens as f/16. The second important thing to be considered while using the Sunny 16 rule is that the shutter speed of your camera should correspond to the ISO value set on your camera.
Aperture = f/16 | Shutter Speed = ISO
Let’s understand it better. Suppose you are shooting a landscape on a bright sunny day using the aperture value as f/16 and ISO 100 on your camera. In order to get the correct exposure, you should be setting the shutter speed at 1/100 seconds. Similarly, if the ISO value is 200, the shutter speed needs to be set at 1/200 seconds.

What if it is not a sunny day?
It might often happen that the weather conditions are not as per your expectations. Nothing to worry, there is a solution to that as well. All you need to do is keep the shutter speed and the ISO constant and simply change the aperture value as per the lighting conditions.
During a mildly overcast or a hazy day, simply open up the aperture one stop to f/11 and when it is cloudy or raining outside, you need to open up the aperture two stops to f/8. If you are shooting a sunset, set the aperture value at f/4.
On the other side, if you are preparing yourself to shoot landscapes on higher altitudes covered with snow, you would need to close the aperture one stop to f/22. The reason behind using f/22 is that the water and the snow usually appear brighter to the camera because of their reflective qualities. If your lens does not go beyond f/16, simply increase the shutter speed of your camera by one stop, i.e. from 1/100 seconds to 1/200 seconds.
Weather Condition | Shadow Detail | Aperture |
---|---|---|
Snowy | Dark with sharp edges | f/22 |
Clear & Sunny | Distinct | f/16 |
Slightly overcast or Hazy | Soft shadows | f/11 |
Overcast or Raining | Barely | f/8 |
Sunset | No shadows | f/4 |