Back-Button AF changes the way autofocus is activated by separating AF activation from shutter release. Many sports action photographers prefer Back-Button AF because it allows you to stop focusing whenever something momentarily enters the picture area that might interfere with focusing on a moving subject you’re tracking.
You can program your Sony a7, a7R, a7S, a7II, a7RII or a7SII camera for Back-Button AF so that focusing is performed by pressing the AEL button with your right thumb.
Activating Back-Button Focus
1. Choose Menu > Custom Settings > Pre-AF > Off
2. Choose Menu > Custom Settings > Custom Key Settings > AEL Button > AF On.
3. Choose Menu > Custom Settings > Custom Key Settings > AF/MF Button > AF/MF Ctrl Toggle.
4. Choose Menu > Custom Settings > AF w/shutter > Off.
Once you do this, AF will no longer be active when you press the shutter release. Instead, press the AEL button to focus. The shutter button still wakes up the camera with a halfpress, and fires the shutter with a full press.
PLEASE NOTE that in order to select the focus point using the Smart Remote Control app, you must turn AF w/shutter back ON.
Once you’ve set up Back-Button AF, leave the first three settings alone. You only need to change one setting to switch Back-Button AF off and on:
Choose Menu > Custom Settings > AF w/shutter > On/On.
Just remember that this setting refers to normal focusing, so for Back-Button AF: On is Off and Off is On.
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