The other day a friend of mine asked me how to shoot film with a camera that didn’t have a light meter. He had bought a Pentax K1000 but didn’t have a battery for the built in light meter the camera had. I told him, just use the Sunny 16 rule. He had never heard of it. So I figured it would be a great topic to blog about. It is a great way to get the right exposure without having a light meter.
The basic rule of thumb states that if you have a clear, sunny day and your aperture is at f/16, whatever ISO you are using, your shutter speed will be the reciprocal value of that ISO value (ISO X = 1/X seconds shutter speed). So for example, if your ISO is 400 at f/16, then your shutter speed will be 1/400 seconds. If your ISO is 100, then your shutter speed will be 1/100 seconds.
But lets say you want to change the aperture from f/16 to f/11. Then you would lower the shutter speed 1 stop. So on a sunny day if your ISO is 400 at f/16 your shutter speed would be 1/400. If your ISO is 400 at f/11 your shutter speed would be 1/800.
For other weather conditions besides clean and sunny, you can also compensate with the aperture in order to keep ISO and shutter speed at the same value. Here are some of the settings I use below.
Weather Condition - Shadow/Detail - Aperture
Snowy/Sandy - Dark with sharp edges - f/22
Clear & Sunny -Distinct -f/16
Slightly overcast - Soft around edges - f/11
Overcast - Barely - f/8
Heavy overcast - No shadows - f/5.6
Open shade/Sunset - No shadows - f/4