Photography is an art that takes practice, but knowing a few basic rules can simplify the process. One of these rules is the Sunny 16 rule, a simple method for determining the correct exposure in natural light conditions. I remember when I first came across it while reading a post on an analog photography forum, and I thought: “Wait... What?!”. When I tried it out, I was amazed by the results. This technique is particularly useful when shooting outdoors in sunny conditions without using a light meter.

In this article, we’ll explore the Sunny 16 rule, how to apply it at different times of the day, and how to adjust it for varying light conditions. To use it, you’ll need a camera with manual settings (aperture, shutter speed, and ISO). Personally, I believe it’s more useful in analog photography, as modern digital cameras are so advanced that they make this technique almost obsolete.

What is the Sunny 16 rule?

The Sunny 16 rule is a guideline for achieving the correct exposure on sunny days. According to this rule, in full sun, you should set your aperture to f/16, and the shutter speed should be the inverse of your ISO value.

Here’s the basic formula:
Aperture: f/16
Shutter speed: 1/ISO

For example, if you're shooting on a sunny day with ISO 200 film, your ideal settings would be:
Aperture: f/16
Shutter speed: 1/200

This provides good exposure without needing an external light meter or the camera’s auto-exposure system. Don’t worry about what the light meter might suggest—just shoot.

How does the Sunny 16 rule work?

The Sunny 16 rule is based on a simple principle: the more light there is, the less time the shutter needs to stay open to get a good exposure. When the light is strong, like on sunny days, a small aperture (f/16) is ideal to prevent too much light from entering the camera, and the shutter speed adjusts accordingly based on the ISO you're using.

Applying the Sunny 16 rule at different times of the day

The Sunny 16 rule works perfectly on clear, sunny days, but natural light changes throughout the day, and this rule can be adapted to different lighting conditions. Here’s how:

Early morning or late afternoon (Golden Hour)

During sunrise and sunset, the light is softer and warmer than at noon. In these conditions, you can modify the Sunny 16 rule slightly. A good starting point is using an aperture of f/4 instead of f/16.

If you're shooting with ISO 200, your shutter speed should be 1/200 of a second, but with an aperture of f/4 to compensate for the lower light.

Noon or full sun

These are the ideal conditions for applying the Sunny 16 rule exactly. The sun is high in the sky, and the light is intense. In this case, set your aperture to f/16 and adjust the shutter speed based on your ISO:

ISO 100 → 1/100 second
ISO 200 → 1/200 second
ISO 400 → 1/400 second

Partly cloudy skies

When there are some clouds in the sky and the light is filtered, you can adjust the Sunny 16 rule by setting a wider aperture, like f/11. This lets more light into the camera.

For example, if you’re shooting with ISO 400 and there are scattered clouds, you can set:
Aperture: f/11
Shutter speed: 1/400

Cloudy skies

With a completely cloudy sky (but no dark storm clouds), the light is more diffused and less intense. In this case, you can open the aperture further, setting it to f/8.

With ISO 100, your settings could be:
Aperture: f/8
Shutter speed: 1/100

Overcast skies

If the sky is covered with dark clouds and looks like it might rain, the light will be much weaker, so you’ll need to adjust the aperture. In this case, opening the aperture to f/5.6 or f/4 can let in more light.

If your film has an ISO of 200, your settings become:
Aperture: f/5.6 or f/4
Shutter speed: 1/200

Twilight

If you enjoy shooting when the sun is below the horizon, the light will be much dimmer compared to daytime. Here, it's advisable to use an aperture of f/2.8 to capture enough light.

With ISO 100, the settings to use are:
Aperture: f/2.8
Shutter speed: 1/100

How to adapt the Sunny 16 rule to changing light conditions

The Sunny 16 rule can be further adapted to different light conditions using simple exposure stop logic. If the light decreases by one stop (for example, from full sun to cloudy), you can open the aperture by one stop (from f/16 to f/11) or slow down the shutter speed by one stop (from 1/100 to 1/50 second).

Here are some common situations where you might want to adjust the Sunny 16 rule:

• - Sand or snow: If you're shooting in a highly reflective environment, like a beach or a snowy area, close the aperture by one stop to compensate for the reflected light (from f/16 to f/22).
• - Deep shade: In particularly shaded areas or indoors, you may need to open the aperture by two or three stops, going from f/16 to f/8 or even f/5.6.

Practical examples

Imagine you’re in a park at sunset. The light is soft and golden, so instead of using f/16, you set it to f/4. With an ISO value of 100, you adjust the shutter speed to 1/100 second to get a balanced exposure.

In another scenario, on a cloudy day, you find yourself near a building with deep shadows. You can go from f/16 to f/5.6, keeping the shutter speed at 1/100 to maintain the right balance between aperture and available light.

Conclusion

The Sunny 16 rule is a simple yet powerful tool for photographers, especially those who love shooting outdoors. Knowing this rule allows you to take well-exposed photos without relying on light meters or the camera's auto-exposure functions. With a bit of practice, it will become a natural skill, allowing you to focus solely on the creativity of your composition.

Gallery

When I travel, I always rely on the Sunny 16 Rule for its practicality: this way, I can stop worrying about exposure and focus on what's happening around me. Here are a few examples you might find useful. If you want to learn more, check out my posts about my trips to Berlin, Warsaw, and the Camargue.