By default, the button is set to lock autofocus and autoexposure together and to keep them locked as long as you keep your finger on the button. But you can also set things up so that the button locks exposure only or focus only.
Change the AE-L/AF-L button behavior by choosing Buttons from the Setup menu, and then selecting Assign AE-L/AF-L Button, as shown on the left here. Press OK to display the available settings, shown on the right.
The options produce these results:
- AE/AF Lock: This is the default setting. Focus and exposure remain locked as long as you press the button.
- AE Lock Only: Autoexposure is locked as long as you press the button; autofocus isn't affected. (You lock focus by pressing the shutter button halfway.)
- AE Lock (Hold): A single press of the button locks exposure only. Exposure lock remains in force until you press the button again or the Standby Timer delay time expires.
- AF Lock Only: Focus remains locked as long as you press the button. Exposure isn't affected.
- AF-ON: Pressing the button activates the camera's autofocus mechanism. Whether focus is locked or continuously adjusted depends on the Focus mode setting. If you use the AE-L/AF-L button to set focus, pressing the shutter button activates exposure metering only.