Controlling Light

Aperture (2, 2.8, 4.0, 5.6, 8, 11, 16, 22, 32)
Measured in ƒ-stops.
Moving from smaller number to larger number cuts the amount of light in half.
Moving from larger number to smaller number doubles the amount of light.

Shutter speeds (1, 2, 4, 8, 15, 30, 60, 125, 250, 500, 1000, 2000, 3000, 4000)
Measured in seconds.
Moving from smaller number to larger number cuts the amount of light in half.
Moving from larger number to smaller number doubles the amount of light.

ISO (100, 200, 400, 800, 1600)
Same as film speed.