An adjustable-focus PV (picture/video) camera in a mixed-reality head-mounted display (HMD) device operates with an auto-focus subsystem that is configured to be triggered based on location and motion of a user's hands to reduce the occurrence of auto-focus hunting during camera operations. The HMD device is equipped with a depth sensor that is configured to capture depth data from the surrounding physical environment to detect and track the user's hand location, movements, and gestures in three-dimensions. The hand tracking data from the depth sensor may be assessed to determine hand characteristics—such as which of the user's hands or part of a hand is detected, its size, motion, speed, etc.—within a particular region of interest (ROI) in the field of view of the PV camera. The auto-focus subsystem uses the assessed hand characteristics as an input to control auto-focus of the PV camera to reduce auto-focus hunting occurrences.