If you have been involved in photography for just about any length of time, you’ll probably know about or have heard of the “Sunny 16” rule of exposures. Allow me to recap it before moving into today’s topic pf predictable exposures.
Sunny 16, also know as Basic Daylight Exposure (BDE for short), is the making of a predictable exposure based on the constant brightness level of the sun. Anywhere on the earth where the sun shines and there are no clouds to obscure, the formula works. Simply stated the formula is as follows:
Basic Daylight Exposure Formula (BDE)
Set your camera’s ISO and match number this exactly with your Shutter Speed. Then shoot at f16 for any front lit subject. This accurate as long as there are no interruptions between the sun and the subject and the sun is more than 20 degrees above the horizon. You can also change off of f16 as long as you use the reciprocal aperture/shutter speed combination. For example, 1/60th of a second @f16 is equal to 1/500th of a second at f5.6
Now, here is where the good part comes in. This formula is crazy accurate because the brightness of the sun doesn’t change. It is the constant on which the formula is built, so to speak. Well, if this is true then there must be other constant brightness sources and situations we can use to our advantage….and there are a lot of them. Take a look at the following chart.
As you begin to test these settings in your camera for the different situations, I encourage you to consider which of the controls are most important based on that specific subject. For example, a skyline picture of NYC at night from NJ side of the river might require f16 for depth of field. In that case, if you are using ISO 125, count ten stops back from 125th of a second, so you would go from 1/125th, 1/60th, 1/30th, 15th , 1/8th, 1/4th , 1/2 , 1 sec, 2 sec, 4 sec, 8 sec. This resulting exposure would be 8 Seconds at f16. This is one of those case where you cannot really meter a night shot of a skyline so this type of predictability is highly important.