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.

Text & Photos By David Coleman
Last Revised & Updated:
Filed Under: Glossary

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Quick Summary

  • The Sunny 16 Rule is a guideline for setting camera exposure in bright sunlight without using a light meter.
  • The basic principle: set the lens aperture at ƒ/16 and the shutter speed to the reciprocal of the ISO.
  • For example, with ISO 100, use a shutter speed of 1/125.
  • The rule can be adjusted for various lighting situations by changing the aperture (see chart below for reference).
  • While once essential in early SLR photography days, it’s now mostly nostalgic due to built-in light meters in modern cameras.

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.

Exposure Calculator

Here’s an alternative tool. Again, these are very much starting points, and individual lighting conditions might (or will) require adjustment.

Dynamic Exposure Guide

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!

FAQs on the Sunny 16 Rule

What Is the Sunny 16 Rule?

The Sunny 16 Rule is a guideline for setting the camera exposure in bright sunlight without a light meter, where you set the aperture to f/16 and match the shutter speed to the reciprocal of the ISO.

How Do I Adjust the Rule for Overcast Conditions?

In overcast conditions, you typically open the aperture one or two stops (e.g., f/11 or f/8) while keeping the shutter speed and ISO settings constant.

Can I Use the Sunny 16 Rule with Digital Cameras?

Yes, the Sunny 16 Rule can be applied to digital cameras. It’s a useful skill to understand exposure, especially if you’re shooting in manual mode or if your camera’s light meter fails.

Is the Rule Applicable to All Types of Photography?

While the rule is a great starting point, it’s not universally applicable. For instance, in action or wildlife photography, you might prioritize shutter speed over aperture settings in order to ensure that you’ve frozen the action with a sharp photo.

How Accurate Is the Sunny 16 Rule?

The rule is more of a starting point that a true rule. Modern cameras offer more precise metering technologies, but the Sunny 16 Rule remains a helpful guideline, especially in challenging light conditions.

What If My Camera or Lens Doesn’t Have f/16 Aperture?

If your camera doesn’t support f/16, use the nearest available setting and adjust the shutter speed or ISO accordingly to balance the exposure.

Can the Rule Be Used for Indoor Photography?

The Sunny 16 Rule is primarily for outdoor lighting conditions. Indoor settings often require different considerations for light sources and intensities. What might look like a bright scene indoors might not be anywhere near the brightness of an outdoor scene; it’s just that your eyes have adjusted to the lower light levels.

How Do I Modify the Rule for Snowy or Sandy Environments?

In these highly reflective environments, consider stopping down the aperture to f/22 to prevent overexposure.

  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.[]
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David Coleman

I'm a professional photographer based in Washington, DC. Seven continents, up mountains, underwater, and many places in between. I've been shooting for 30+ years, and my photos and time-lapse videos have appeared in a bunch of different publications, from major newspapers to magazines and books, billboards, TV shows, professional sports stadiums, museums, and even massive architectural scrims covering world-famous buildings while they're being renovated. You can see some of my travel photography here and here.

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