Sunny 16 – A Rule of Thumb

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“Sunny f/16″, or “Sunny 16″, is a mnemonic to help photographers recall a “rule of thumb” for estimating correct daytime exposure. Initially established for film photography (which is an obvious statement, since most “rule of thumbs” that have been around for a while, such as this one, were based in film photography) to help estimate exposure without the use of a light meter, “Sunny 16″ can also be applied to digital photography.

The basic rule states that on a sunny day, the photographer should set the aperture at f/16, and set the shutter speed at about the same number in hundredths of a second, as the ISO being used. For instance, if the photographer is shooting at ISO 100, the shutter speed should be around 1/100 to 1/150. ISO 200, shutter speed around 1/200 to 1/250, etc.

The correspondence of f-stop, ISO, and shutter speed can be applied to any light conditions:

f/16 – Sunny, distinct shadows
f/11 – Somewhat overcast, shadows are soft around edges
f/8 – Overcast, shadows are barely visible
f/5.6 – Very overcast, no shadows

With the auto-exposure features available in today’s digital cameras, it’s easy to allow our camera to do all the work. Still, it’s beneficial every now and then to remind ourselves of the how’s and why’s when composing our shots.

Photo Credit: “Sunny Day” by jhoc on Flickr Creative Commons.

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