The Exposure Guide in a box of Kodak Film. Introduction to the Sunny 16 Rule. Shot with the sun going down at the harbour in Cefal, Sicil ! The Sunn "# rule SUNNY 16 RULE. When caught without a meter, one can use the "Sunny 16 Rule" as a guide for exposure. There are two steps to the rule, as outlined below:. If you're into photography, you've likely heard of the "sunny 16 rule." Find out what it is and how you can get perfect exposures without a light meter! The basic rule is, "On a sunny day set aperture to f/16 and shutter speed to the [reciprocal of the] ISO film speed [or ISO setting] for a subject in directIt's simple: Sunny 16 says that on a sunny day, you should set your aperture to. F16 and your shutter speed to the reciprocal of your film speed, This is a great rule to follow for outside natural light shooting. It works very well, and you can bracket (make exposures + or – one stop so you will have Sunny Rule f/16. What is the Sunny f/16 Rule? The Sunny 16 Rule is a way to meter for correct exposure during daylight without using the camera's meter. The Sunny 16 Rule is a way to meter for correct exposure during daylight without using the camera's meter. So for example, if your ISO is 200 at f/16, then