Sunny 16 rule
When you do not have a light meter, the "Sunny 16 rule" or "Sunny f/16 rule" is a method to estimate correct daylight exposure. The Sunny 16 rule can also help to determine aperture and shutter speed settings when conditions are not typical sunny days.
Rules
- Set your shutter speed equal to your film speed. (Shutter = Film Speed)
- Set your aperture equal to f/16 for sunny sky.
| Aperture | Lighting Conditions | Shadow Detail |
| f/16 | Sunny | Distinct |
| f/11 | Slightly Overcast | Soft around edges |
| f/8 | Overcast | Barely visible |
| f/5.6 | Heavy Overcast | No shadows |
What if it's not sunny?
If the lighting conditions are slightly overcast, open one stop to f/11. If overcast, open two stops to f/8. If deeply overcast, open three stops to f/5.6.
How do I distinguish between slightly overcast, overcast and heavy overcast?
Examine the shadow detail. If shadows are distinct but soft around the edges, then it's slightly overcast. If shadows are not distinct, but still visible – very soft – then it's overcast. If there are no shadows at all, then it's heavy overcast.
