Photography and the f16 Rule

If you’ve been practicing photography for any length of time, undoubtedly you’ve come across the f16 rule or the Sunny 16 rule that states that on a sunny day at noon, if your aperture is set to f16, then the proper shutter speed to use in the reciprocal of the ISO. Therefore, if your ISO is 100, then the proper shutter speed is 1/100. Basically, this rule helps you sum up and remember exposure settings so that you can enhance the photos you take without having to rely on automatic settings. Getting out of “auto” and into “manual” is one of the first steps to becoming a better photographer and the f16 rule is one that all photographers can swear by.

This rule also works regardless of where you are when you take your photos or what kind of SLR camera you’re using. Every SLR camera manufacturer builds this rule into their cameras as it is pretty much a standard when it comes to exposure and metering. In fact, the f16 rule is so versatile that there are only two times it needs to be modified — when photographing in a very snowy or very bright sandy environment where the sun is reflected back by the natural landscape. In those cases, f16 becomes f22 since the amount of light is effectively doubled.

Why should you care about this rule at all? Because learning to make proper use of it is the key to capturing better and better images. It allows you to take control of the camera instead of being at the mercy of the auto mode. So, if you’ve ever taken a photo of a shaded setting but had bright light in the background, causing the photo to come out underexposed, you can use the f16 rule to figure out the best settings to use to capture the colors in the shade regardless of the more distant background light. Additionally, if you’ve ever gotten an overexposed image because of the brightness of the immediate light source, then you can make use of this rule to dial down the exposure a bit, getting the image you wanted to capture instead of the one that your camera tried to guess you wanted.

If you’re still uncertain of how best to calculate which ISO and shutter speed to use, feel free to consult this handy chart for various scenarios. And, feel free to adapt and play with the settings a bit until you feel comfortable with the images you’re getting.

Aperture Lighting Scenario
f/22 Layer of Snow or at The Beach, Sunny Day
f/16 Sunny Day at Noon
f/11 Slightly Overcast
f/8 Overcast
f/5.6 Storm Clouds
f/4 Open Shade / Sunset

— da Bird