Glossary
Sunny 16 rule
Also called: Sunny 16
On a sunny day, set your aperture to f/16 and shutter to the reciprocal of your ISO.
Sunny 16 is the no-meter exposure heuristic that says: in bright sun, f/16 at 1/ISO is correct. So ISO 400 film in full sun shoots fine at f/16 and 1/400 second. The rule scales for cloudy (f/11), overcast (f/8), heavy shade (f/5.6), and sunset. Knowing Sunny 16 means you can shoot even when the meter is unavailable, and it is the most popular training exercise in the app.