Back-button focus separates autofocus activation from shutter release. The shutter half-press no longer engages AF. Instead, the AF-ON button on the rear of the camera acquires and holds focus. It is the single camera configuration change that most noticeably improves shooting consistency, and the RF 24-105mm f/4L IS USM — the kit lens for most R5 and R6 kits — is where most photographers should learn it. The mechanics: hold AF-ON to focus continuously on a moving subject.