Back-Button Focustechnical
Moving focus off the shutter button onto a rear button, so focusing and shooting are separate.
By default a half-press of the shutter both focuses and meters. Back-button focus assigns focusing to a dedicated rear button (often AF-ON). Now the shutter only takes the picture. This lets you lock focus once and recompose freely, hold focus on a still subject, or track a moving one continuously — without the camera re-focusing every time you shoot. It feels odd for a day, then most people never go back.
Use this when
- Wildlife / action: hold the button to track
- Focus + recompose: tap once, release, recompose
Common mistake: Pressing the shutter expecting it to focus, after enabling BBF — it no longer does.