Looney 11 rule is a method of estimating correct exposure without a light meter at night. It can also be helpful with difficult subjects. How to use Looney 11 rule? First, set your aperture (f-stop) to f/11. Next you need to select your ISO. Finally, set your shutter speed to 1/ISO. If ISO 100 is used, then shutter speed is 1/100. In case your camera doesn't have 1/100 shutter speed as an option, you can use 1/125 instead. Aperture or shutter speed can be changed to correspond to your needs as long as you compensate by changing the value of the other as well. For example, 1/250 second at f/8 gives equivalent exposure to 1/125 second at f/11.
Lighting Condition
Aperture
Full Moon
f/11
Half Moon
f/8
Quater Moon
f/5.6
Crescent Moon
f/4
Total Eclipse
f/2.8
Star Gaze
f/2
Backlighting
Add one stop
For daytime photography there is a similar rule known as the Sunny 16 rule.
