What is the Sunny 16 Rule?

If you’ve ever seen mention of the Sunny 16 Rule and wondered what it means, here’s an explanation.

Filed Under: Glossary

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The Sunny 16 Rule turns up on photography T-shirts, photography mugs, and even bumper stickers. But one place it really doesn’t turn up much anymore is when actually taking photos.

That wasn’t always the case. At one point in time, it was useful. These days, it’s mostly a nostalgic remnant of the early days of SLR photography.

The Sunny 16 Rule isn’t really a rule in a technical sense. It’s a rule of thumb, which gave you an approximation of a decently exposed photo in the days before SLR cameras, and certainly DSLR cameras, had built-in light meters. And it was a staple of making photography less daunting for newcomers, which is why it featured prominently in guides like Kodak’s ubiquitous (and remarkably useful) field guides.

The rule goes along these lines:

When taking a photo in bright sunlight, set the lens aperture at ƒ/16 and set the shutter speed to the reciprocal of the ISO.

So, if you were using a film with an ISO (or ASA) of 100, you’d use a shutter speed of 1/125, which was the closest shutter speed to 1/100 at the time. 1

The “reciprocal” part sounds complicated, but it’s really not. It’s as simple as just adding “1/” to it and round to the closest available shutter speed. In other words:

  • If your film is ISO/ASA 100, use a shutter speed of 1/125.
  • If your film is ISO/ASA 200, use a shutter speed of 1/250.
  • If your film is ISO/ASA 400, use a shutter speed of 1/400.

And so on.

Adjusting the Sunny 16 Rule for Different Lighting Situations

The Sunny 16 Rule is really just a baseline (and an approximate one, at that). And it leads to a series of variations.

Obviously, not all photos are taken in full sunshine. But there’s a straightforward way to adjust it for some common lighting situations to get close to a good exposure.

The gist is that you start with the Sunny 16 Rule. Then adjust only the aperture for different lighting.

Sunny 16 Rule Chart

Scene Aperture
Bright sunshine on snow or light sand ƒ/22
Bright sunshine with strong shadows ƒ/16
Hazy sun (indistinct shadows) ƒ/11
Cloudy bright (no shadows) ƒ/8
Backlit subject in bright sunshine ƒ/5.6
Heavily overcast skies ƒ/5.6
Open shade (ie. the subject is in the shade but bright open sky is providing the illumination) ƒ/5.6
Sunset / Golden Hour ƒ/4

There are obviously a bunch of limitations of this. It gives you no real power to control depth of field with a wider aperture or the account for fast-moving subjects that might call for a faster shutter speed. Those types of situations can be calculated from the starting baseline, but they start adding complications that stretch the Sunny 16 Rule beyond its usefulness as a simple rule of thumb.

Is the Sunny 16 Rule Still Useful?

The Sunny 16 rule is really a throwback to film SLR days, and even then, early film SLR days. It’s most relevant when you don’t have a light meter, but light meters have been pretty standard in cameras since the mid to late-1960s. Although, one of the fun things about SLR cameras of that era is that the light meter was a standalone feature and the only one that required a battery. If you didn’t bother to replace the light meter’s battery, the camera otherwise worked completely normally.

For the last 50-60 years, internal light meters have been standard issue in film cameras. And they’re essential in digital cameras.

So the Sunny 16 isn’t really relevant or that useful today except for fringe cases such as experimenting with photography fundamentals or using a very old film camera. But it does make for a fun T-shirt!

  1. ISO and ASA are both standards used to measure the sensitivity of film or a digital sensor to light in photography, but they come from different times and standards organizations. You’ll mostly come across ASA in film photography circles. It stands for American Standards Association, which is now known as the American National Standards Institute (ANSI). ASA was used to denote film sensitivity before digital cameras came into existence. The higher the ASA number, the more sensitive the film was to light, meaning it would require less light to properly expose an image. With the advent of digital cameras, the International Organization for Standardization introduced a more comprehensive scale for light sensitivity, known as ISO. It is equivalent to the ASA scale, but the ISO standard includes more information than the ASA standard did. ISO has two parts: one that refers to the speed of the film (akin to ASA) and another that refers to the grain or noise that could be expected. For example, ISO 200/24° means the film or sensor has a speed rating of 200 and a 24° grain rating. In modern usage, especially with digital cameras, you will most often encounter ISO rather than ASA. However, in film photography circles, the term ASA might still be used.[]
David Coleman / Photographer

David Coleman

I'm a professional freelance travel photographer based in Washington DC. Seven continents, up mountains, underwater, and a bunch of places in between. My images have appeared in numerous publications, and you can check out some of my travel photography here. More »

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