Choose whether exposure locks when the shutter-release button is pressed.

Option Description
O On (half press) Pressing the shutter-release button halfway locks exposure.
P On (burst mode) Exposure only locks while the shutter-release button is pressed all the way down.
  Off Pressing the shutter-release button does not lock exposure.

A Custom Settings: Fine-Tuning Camera Settings

a: Autofocus

b: Metering/exposure

c: Timers/AE lock

d: Shooting/display

e: Bracketing/flash

f: Controls

g: Movie