You are out with your family on a bright sunlit day. The kind of day on which photographers prefer using the Sunny 16 Rule. In case you are not familiar with the Sunny 16 Rule, it is a simple age-old exposure guideline that helps you to set the correct exposure on a bright sunny day. But what is this Sunny 16 Rule? And how does one use this rule in photography? Let’s look at a few ways on how to tweak the Sunny 16 Rule in photography.
The Sunny 16 Rule states that when you are outdoors on a bright sunny day your aperture should be at f/16. The ISO should be set to the lowest possible on your camera. The final element of the exposure triangle, shutter speed should be set to the inverse of the ISO; which means 1/100, considering ISO 100 is the lowest possible on your camera.
Tweak the Sunny 16 Rule to Freeze Movements
But the Sunny 16 Rule seems kind of rigid, in terms of the shutter speed that you can use. What if the subject is moving really quick and you want to freeze it? Let’s say your kids are playing on the beach or on the snow and you want to freeze their movements. With a shutter speed of 1/100 this seems quite impractical.
As I mentioned before the Sunny 16 Rule is an exposure guideline in a certain lighting condition. You can take it as the general exposure guide and then tweak it to fit your needs. Let’s say you feel that a shutter speed of 1/400 is going to be good enough to capture a sharp image of your kids playing. Thus, going by the Sunny 16 Rule your shutter speed should be the inverse of ISO, you need a corresponding ISO of 400 to make a proper exposure. There you have it. You‘ve successfully tweaked the Sunny 16 Rule!
Create shallow depth of field
Ok. Let’s take another scenario on how to tweak the Sunny 16 Rule. The Sunny 16 Rule with its f/16 aperture guideline sets a large depth of field on the outset. A large depth of field brings a large part of the scene acceptably sharp. What if you don’t need a large part of the scene to be acceptably sharp? What if you want to have a slightly soft background for a portrait image?
We have learnt earlier that aperture and shutter speed has an inverse relationship. When you change the aperture and use a wider setting, shutter speed has to speed up to compensate that change and vice versa. In this example to have a slightly softer background you will need to use a wider aperture (wider aperture = shallower depth of field). Let’s say you stop down the aperture to f/8 (an increase of two stops from f/16). When you do that you will need to speed up the shutter speed to maintain the same exposure. The new shutter speed thus, will be two stops faster, 1/400.
The Sunny 16 Rule was devised before the digital era. It was devised as a guideline for photographers who did not have the luxury to review an image after it was made and to verify whether the exposure is correct or off. They could only find that out a day later when the film was developed and a print was made. Digital shooters are way better off. But despite the technical progress made the Sunny 16 Rule is still relevant, especially for those who shoot manually.