Choose whether the shutter-release button can be used to focus. If [AF-ON only] is selected, the camera will not focus when the shutter-release button is pressed halfway. Focus can only be adjusted using other controls to which AF-ON has been assigned using Custom Setting f2 [Custom controls (shooting)].
To choose whether the shutter can be released even in circumstances in which it would normally be disabled, select Custom Setting a6 [AF activation], highlight [AF-ON only], and press 2. Selecting [Enable] allows the shutter to be released at any time.